For the Cake:
2 /4 c. cake flour, sifted
2 tsp. baking powder
1/2 tsp. salt
1/2 lb (2 sticks) butter
2 cups sugar
4 large egg yolks
2 tsp. vanilla
1 cup sour cream
4 large egg whites
zest of 2 lemons
1 1/2 tsp. almond extract
1 tsp. lemon extract (opt).
Preheat the oven to 350. Prepare 2-8 inch cake pans. Sift together flour, baking powder and salt. Cream together butter and sugar until light and fluffy. Add yolks, one at a time. Add extracts and lemon zest. Add flour mixture in fourths alternately with sour cream in thirds. Beat egg whites till soft peaks. Gently fold into batter and pour into pans. Bake 45-60 minutes or until done.
For the Lemon Curd filling:
3/4 c. fresh lemon juice
1 Tbsp. lemon zest
3/4 c. sugar
3 large eggs
4 Tbs. butter
Whisk all ingredients except butter in a saucepan over moderately low heat. Cook, stirring constantly, for 5-10 minutes, till curd is thick and pudding-like. Strain into a bowl and whisk in butter a little at a time. Refrigerate at least 2 hours.
(So this is delicious lemon curd, but it was a little too soft as a cake filling. I would recommend some extra thickening, such as 1-2 Tbs. corn starch, but I haven't tested that yet.)
For the Lemon Buttercream:
5 large egg whites (for food safety you can also sub meringue powder + water as in instructions on pkg.)
1 1/4 c. sugar
1/2 c. + 2 Tbs. corn syrup
2 c. butter, at room temperature
1 Tbs. lemon zest
1/4 c. + 2 Tbs. lemon juice
Place the egg whites in the clean bowl of a stand mixer fitted with the whisk attachment and whisk on medium high speed until foamy. Sprinkle in 6 Tbs. of the sugar and beat on high speed to medium peaks (the whites should be smooth, full, shiny, and the peaks should curl a little. Turn off the mixer.
Combine the remaining 3/4 c. plus 2 Tbs. sugar and the corn syrup in a medium saucepan over medium high heat, stirring briefly to dissolve the sugar. Cook just until it comes to a rolling boil.
Immediately remove the syrup from the heat, turn the mixer onto medium-high speed, and slowly pour the syrup down the side of the bowl in a steady stream, being very careful not to let the syrup hit the whisk.
Reduce the speed to medium and continue whisking until the whites are barely warm, 5-7 minutes. Add the butter 1 Tbs. at a time. (I think the original recipe had too much butter, so I've reduced it here by 1/2 cup. Taste after you've added the first 1 1/2 cup and then add the remaining butter as desired) Add the lemon zest and juice and continue beating until the frosting is smooth and creamy.
This makes a LOT of buttercream. I might recommend you cut the recipe by half, especially if you're going to do a semi-naked cake.
To Assemble:
Fill the cooled (or better yet, frozen) cake layers with the lemon curd. Frost with the buttercream. Garnish with candied lemon peel.