This layered confection pairs subtly lemon, tender cake with rich, sweet, tart lemon buttercream. The result is a truly tasty lemon experience reminiscent of sipping lemonade on a hot summer day.
Preheat the oven to 325°F. Lightly grease and flour two 9" round pans or two 8" square pans; or line them with lightly greased parchment, if desired.
To make the cake: Beat the butter, sugar, and oil until the mixture lightens in color and texture, 2 to 3 minutes at medium speed.
Beat in the baking powder, salt, enhancer, vanilla, and lemon juice powder.
Add the egg whites and the whole egg a little bit at a time, scraping the bottom and sides of the bowl as needed in between additions. Beat until the mixture is fluffy, then scrape the bottom and sides of the bowl again and beat briefly to recombine any sticky residue.
Add the flour in three additions, alternating with the yogurt or milk. Scrape the bowl after each addition; the mixture should be fluffy when done.
Stir in the color, if you're using it.
Scoop the batter into the prepared pans. Wrap the pans in cake strips, if you have them, to prevent doming.
Bake the cakes for 30 to 35 minutes, until a cake tester or toothpick inserted into the center comes out clean.
Remove the cakes from the oven, and cool them in the pans for 10 minutes before turning them out onto a rack to cool completely.
To make the frosting: Dissolve the granulated sugar in the boiling water; cool completely.
Using an electric mixer (hand, or stand), combine the cooled sugar syrup with the meringue powder and beat until soft peaks form.
Add the confectioners' sugar, stirring until thoroughly combined.
Add the butter and beat until creamy. Stir in the lemon powder and oil, then the salt.
To assemble the cake: Spread the frosting onto the top of one layer of cake. Top with the second layer, and frost the top and sides of the whole cake.
Storage information: Store leftover cake, well wrapped, at room temperature for several days. Freeze for longer storage.
