Key Lime Cake is an delicious dessert, with two layers of moist cake, tangy lime curd filling and fluffy cream cheese frosting. Use my recipe and helpful tips to make this stunning and delicious holiday show-stopper!
Citrus fruits are typically available any time of the year, but Key limes have the best flavor in late summer and fall.
Unlike Persian limes (the kind you typically find in the grocery store), Key limes are smaller, rounder, and a bit sweeter. The flavor is vibrant and seriously delicious!
Why You'll Love This Recipe
- Tangy and refreshing flavors. The citrus flavors in the cake, frosting, and curd are what make this Key Lime Cake so delicious!
- Tastes better than a store bought dessert: The layer cake is super moist, and tastes better than anything you can buy from the store!
- Easy, yet impressive: Even though this cake looks over the top, I promise you, it's easy to make, even if you aren't a pro baker!
Other favorite citrus dessert recipes include Lemon Poppy Seed Cake and Lemon Bars.
Ingredients
See ingredient substitutions in the next section. ⬇️
Here's what you'll need to make the cake, curd, and cream cheese frosting:
To make this key lime cake, you'll need:
- all-purpose flour: I like to use unbleached AP flour because it's less processed, but bleached flour is perfectly fine to use.
- leaveners: You'll need baking powder and baking soda. If you haven't used them in a while, it's best to test them for freshness.
- salt: Be sure to use a coarse grain like kosher or sea salt. Do not use iodized table salt!
- canola oil
- unsalted butter: If you can afford it, I recommend using European butter rather than American-made. The extra butterfat content creates better flavor.
- white granulated sugar
- large eggs and egg yolks: Egg yolks are one of the primary ingredients in lime curd. The fresher the eggs are, the better the consistency of the curd will be.
- whole milk
- vanilla extract
- cream cheese: For the fluffiest frosting, use block-style, full fat cream cheese.
- powdered sugar
📖 Time-Saving Tip - Testing Baking Soda or Baking Powder for Freshness
This simple little test can save you time and money, because if your leavener is expired, whatever you're baking wont rise in the oven! This test works for baking soda and baking powder:
- Add about ½ teaspoon of baking soda or powder to a small bowl. Stir in an equal amount of an acidic ingredient, like vinegar or citrus juice.
- If the solution doesn't start to bubble immediately, it's time to replace your leavener.
Substitutions and Recipe Variations
- all-purpose flour: For a lighter crumb, you can substitute 1 cup of cake flour for 1 cup of all-purpose flour. If you'd like to make the key lime cake gluten-free, substitute the AP flour with a cup-for-cup variety of gluten-free all-purpose flour. Two popular brands are Bob's Red Mill and King Arthur Flour.
- baking powder: If you happen to be out of baking powder, but you have baking soda and cream of tartar on hand, you can make a baking powder replacement!
To use baking soda as a substitute for baking powder, mix ½ teaspoon of cream of tartar with ¼ teaspoon of baking soda for every 1 teaspoon of baking powder. - white granulated sugar: To reduce the calories, you can substitute the sugar with any cup-for-cup variety of granulated sugar substitute. Monkfruit sugar is a good option.
- oil: Using a neutral-flavor of oil like canola or vegetable ensures moisture without altering the key lime flavor.
- unsalted butter: If you need or want to use salted butter, just omit the ¼ teaspoon of salt this recipe calls for. I do not recommend using plant-based substitutes.
- limes: I recommend using fresh juice and zest for this recipe. You don't have to use key limes. You can use regular Persian limes, or substitute lemons, like in this Lemon Curd Cake.
Look for limes that have a smooth skin, feel heavy for their weight, and give slightly when pressed with your fingers. These will yield the most juice. Those that are hard and have a more dimpled skin are not as juicy. - eggs: Egg yolks are important for creating moisture and structure in the cake, and should not be substituted.
- milk: You can substitute whole milk with half and half, low fat milk or non dairy milk.
- vanilla extract: If you need an alcohol-free flavoring, you can use vanilla essence.
For more tips on changing the cake's consistency, see my post, How to Make a Cake More Moist.
How to Make Key Lime Cake
Summary only. The complete recipe instructions are in the card at the bottom of this post ⬇️
- Make the cake batter. You can use an electric hand mixer or a stand mixer.
- Bake in parchment-lined baking pans.
Make the Lime Curd
- Simmer sugar with lime juice and zest.
- Temper in the eggs and egg yolks.
- Cook until thick and glossy.
Frosting Key Lime Cake
- Make cream cheese frosting.
- Frost just the tops of both layers.
- Add lime curd to the top of the cake.
- Garnish the key lime cake.
Liz's Tips for the Best Tasting Dessert
- For the moistest cake, be sure to use room temperature ingredients, including refrigerated items like eggs and cream cheese.
- To prevent sticking, line the inside bottom of the baking pans with parchment paper.
- This layer cake is meant to be bare on the sides. To completely frost the outside of the cake, you will need to make a double batch of cream cheese frosting.
- Curd: If you prefer a completely smooth curd, you can refrain from adding the second round of zest after you strain it out. I like the flecks of citrus zest in the curd, as it lets people know right away that it is lime curd.
- Want to make cake ahead? The layers can be baked up to 2 days ahead of time. Keep them in the fridge, tightly wrapped in plastic, until you're ready to frost.
Storing and Freezing
Storing: Wrap any leftovers tightly in plastic wrap or in an airtight container. In the fridge, the key lime cake will stay fresh for up to 5 days . Do not store the dessert at room temperature - the lime curd needs to be kept in the fridge!
Freezing: The assembled layer cake will not freeze well, as the lime curd can weep excess moisture when thawed.
However, you can freeze the undecorated layers for up to 3 months. Just double wrap each layer separately in plastic wrap and aluminum foil to prevent freezer burn.
Leftover lime curd can be used to make other desserts and/or served in other ways. It's delicious stirred into yogurt, spread on toast, pancakes or waffles. In a tightly sealed jar or container, lime curd will keep in the fridge for up to 2 weeks.
Key Lime Cake Recipe FAQ
Because Persian limes are more potent than Key limes, using them as a substitute requires an adjustment. Use 2 to 3 times less than the amount of Key lime called for in the recipe.
A crumb coat is a thin layer of frosting that “locks in” crumbs before applying the final coat. It isn't necessary for this recipe because the layers aren't completely covered in frosting.
Either freezing or chilling the layers in the fridge for 20-30 minutes can make them sturdier and easier to frost. This is especially helpful if your cake is very soft or you are frosting in warm weather.
Key Lime Cake
Ingredients
Cake
- 1 ⅓ cup whole milk room temperature
- 1 tablespoon lime juice key lime or regular lime
- 2 cups all-purpose flour spooned and leveled
- 1 teaspoon baking powder
- ½ teaspoon baking soda
- 1 teaspoon sea salt
- 1 cup canola oil
- 2 cups granulated white sugar
- 3 large eggs room temperature
- 2 tablespoons lime zest key lime or regular lime
Lime Curd
- 1 tablespoon lime zest divided
- ½ cup lime juice
- 1 cup granulated white sugar
- ¼ teaspoon sea salt *omit if using salted butter
- 3 large eggs room temperature
- 2 large egg yolks room temperature
- ¼ teaspoon vanilla extract
- 4 tablespoons unsalted butter softened and cut into small pieces
Cream Cheese Frosting
- ½ cup unsalted butter softened
- 8 oz cream cheese softened
- 1 teaspoon vanilla extract
- 1 tablespoon lime zest
- ¼ teaspoon sea salt *omit if using salted butter
- 4 cups powdered sugar
- 1-2 tablespoons milk if needed.
Instructions
- Preheat the oven to 325℉. Line the bottom of two 9-inch round cake pans with parchment paper and spray with non-stick cooking spray. Set aside.
- Stir lime juice into the milk and set aside. *This will become a buttermilk of sorts, to tenderize the cake. In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
- Add canola oil, sugar, lime zest, eggs, and milk mixture to the bowl of a stand mixer fitted with a paddle attachment (or use a large mixing bowl and handheld electric mixer). Using medium-high speed, beat ingredients to combine.Add in the flour mixture and mix on low speed until just combined. *The cake batter will be relatively thin.
- Divide batter evenly between the prepared pans. Bake on the center rack of preheated oven for 20-30 minutes or until the cake springs back when lightly pressed, and a toothpick inserted in the center comes out clean. Cool cake completely before assembling. Meanwhile, make the lime curd.
Make the Curd
- To a medium saucepan over medium heat, add lime juice, half of the zest, sugar and salt. Stir to combine, then cook until the sugar dissolves and mixture starts to bubble. In a medium heat proof bowl, whisk together the eggs and yolks.
- Carefully and very slowly while whisking constantly, pour three-fourths of the hot lime juice mixture into the eggs. Whisk this mixture back into the saucepan and turn the reduce heat to medium low. Whisk constantly until the mixture thickens enough to coat the back of the spoon, about 8 minutes. Do NOT let this mixture boil.
- Remove pan from heat and pour the mixture through a fine mesh strainer into a bowl. Gently fold butter, vanilla and remaining lime zest into the hot mixture. Cool mixture. Cover the bowl with a layer of plastic wrap directly against the curd to prevent a skin from forming. Refrigerate until you're ready to assemble the key lime cake.
Make the Frosting
- In a large mixing bowl with the mixer on medium-high speed, cream together butter and cream cheese until smooth. Add in zest, vanilla and salt. Reduce mixer speed to low and carefully beat in the powdered sugar, 1 cup at a time. Continue to beat until frosting is smooth and fluffy, about 2-3 minutes, thinning it out with a little milk if necessary.
To Assemble:
- Place the cake on a serving plate/platter. Spread about one-third of the frosting on the top of bottom layer and smooth evenly to the edge. Top with the 2nd cake layer and spread another one-third of frosting over the top. Place the remaining frosting into a piping bag and pipe a thick border around the top edge of the cake. You can use any piping shape you like for the border as long as there are no breaks in the decoration. This creates a wall of frosting to hold the curd in the center.
- You can also place all of the frosting in a piping bag and use a round tip to fill and top the cake. Place as much curd as you’d like into the center of the cake and smooth out to the border. (You will likely have leftover curd. If so, store in a covered container in the fridge for another use.)
- Garnish top of cake with lime slices and zest, if desired. Chill cake until frosting is firm.
Helpful Notes and Tips From Liz
- For the moistest cake, bring all cold ingredients to room temperature before you start making this recipe.
- To prevent the cake from sticking, line the pans with a circle of parchment paper.
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