These have been my daughter's favorite muffins since she was a child. Tart and lemony, they nearly float away they are so light. Serve them warm....they don't even need butter. The beaten egg whites are the trick to these light-as-air muffins; you'll find the batter somewhat stiff before folding in the whites, so fold carefully and with patience. It will take a bit longer than you're accustomed to, but oh the results! I found the recipe back in the 60's in a Junior League cookbook. Which one, I've long forgotten. I've made them many times in mini muffin form as well, very successfully.
Lemon Angel Muffins
1 cup unsalted butter, room temperature
1 cup sugar
4 eggs, separated, room temperature
2 cups flour
2 teaspoons baking powder
1 teaspoon salt
1/2 cup lemon juice
2 tablespoons grated lemon peel
Cream butter and sugar until smooth and add egg yolks. Beat until light. Sift flour with baking powder and salt. Add alternately with the lemon juice. Fold in grated peel. Fold in beaten egg whites. (do not beat them to stiff peaks) Fill greased and floured muffin tins. Bake 375 for 20 minutes.