This cake is perfect for lemon-lovers: a light, subtle lemon cake paired with a very tart lemon filling. The light and fluffy boiled icing (a.k.a. Seven-Minute Icing) adds just the right amount of sweetness without weighing down the cake's flavors. If you want to kick it up for even more lemon flavor, I have added some options below the recipe.
3 cups Cake Flour
2 1/2 teaspoons Baking Powder
1 teaspoon salt
2/3 Cup unsalted butter, softened
1 3/4 Cups Sugar
2 whole Eggs + 1 yolk
1 1/2 teaspoons Pure Lemon Extract
1 Tablespoon Lemon zest
1 1/4 Cups Milk
Preheat oven to 350 degrees. Grease and line with parchment paper: three 6" or 8" pans (or you can use two 9" pans for a two-layer cake). If using 6" pans, your layers will be thick and you will have a little batter leftover. I usually make a few cupcakes for my kids when this happens.
Cake:
In a large bowl mix together the flour, baking powder, and salt until thoroughly blended. Set aside.
In an electric mixer bowl, combine the butter and sugar. Beat on medium speed until light and fluffy, about three minutes. Add eggs and yolk one at a time, beating for a few seconds after each addition. Add the extract and zest. Now add the flour and milk in alternating batches, starting and ending with the flour. Mix well after each addition. Scrape the bowl down and then beat on med-low for about one minute until fluffy (Do not overbeat).
Bake for 30-40 minutes, until a toothpick inserted in the center comes out clean. (Baking time will depend on the size of your pans).
Filling:
This filling is the same as the filling for my Lemon Meringue Pie recipe, only a smaller portion. If you prefer, you can use a good-quality jar of pre-made Lemon Curd, found in the jam section of most stores.
3/4 Cups Sugar
2 Tbsp Cornstarch
1 Tbsp Flour
dash of salt
3/4 Cup Hot Water
1 Slightly beaten egg yolk
1 Tablesppon Butter
2 teaspoons Lemon zest
2 Tablespoons Lemon juice
Mix Sugar, Flour, Cornstarch, and water in a medium saucepan over medium heat.
Cook until boiling, then reduce heat and cook two minutes, stirring constantly, until thickened. Remove from heat. Mix a small amount (about 1 tsp) of the hot mixture into the egg yolks and stir. Add a little more and stir again (this is to temper the egg yolks so they don't cook and curdle). Then add the yolk mixture back into the pan and cook two more minutes, again stirring constantly, until even thicker. Remove from heat. Stir in butter and lemon zest, then slowly pour in the juice. Cool to room temp before using the filling.
Fluffy Boiled Icing:
Prepare one recipe Seven-Minute Icing
Options for increasing the lemon flavor: Bump up the lemon extract to 2 teaspoons (don't do more than that, though). You can also brush a simple syrup made from 1/4 Cup lemon juice and 1-2 Tablespoons confectioner's sugar over the cake layers before filling and stacking them.