Preheat the oven to 350℉. Line an 8x8-inch baking pan with a sling made with 2 long strips of parchment paper. (Lift the sling to remove the brownies from the pan) Set aside.
Add the sugar and zest to a large mixing bowl. Whisk for 1 minute to combine. Pour in the melted butter and whisk again to combine.
Add the eggs and the lemon juice. Stir until the eggs are completely incorporated.
Fold in the salt and flour. The brownie batter should be thick and wet.
Pour the batter into the parchment-lined pan. Use an offset spatula or the back of a spoon to spread it into an even layer.
Place pan in preheated oven bake and bake for 20 to 25 minutes, or until the edges are golden brown and the center is just set. Remove from oven and transfer to a wire rack to rest until brownies reach room temperature (about 30 minutes)
Optional Glaze: In a small bowl, add the powdered sugar and lemon juice and stir until the glaze is smooth and thick.
Pour the glaze over the cooled brownies and spread it out with a spatula. Top with lemon zest, slice, and serve at room temperature.
Notes
Whisking the eggs quickly into the batter will give the brownies a slightly crunchy top and chewier edges.
If you prefer thinner brownies, use a 9x9 baking pan.
If glaze is too thin, add more powdered sugar 1 tablespoon at a time. If the glaze is too thick, add more lemon juice or milk, 1 tablespoon at a time.