1) Preheat the oven to 350°F. Lightly grease two 8" or 9" round cake pans.
2) To make the cake: Stir together the dry ingredients.
3) Work in the butter until the mixture is evenly crumbly.
4) Beat in the egg whites one at a time followed by the whole egg, beating and scraping the bowl after each addition.
5) Gently beat in the lemon juice; then the milk, in two additions. Stir in the food coloring. Pour the batter into the pans.
6) Bake the cakes for 25 to 35 minutes, until a toothpick inserted into the center of one comes out clean.
7) Cool the cakes in the pans for 10 minutes, then transfer them to a rack to cool completely.
8) To make the frosting: Beat together the butter, salt, and meringue powder.
9) Add the remaining ingredients and beat until light and fluffy.
10) Frost the top of one layer, top with the second layer, and frost the whole cake as desired.
Yield: one 8" or 9" round layer cake.