In a mixer bowl cream the egg yolks, butter and sugar using a mixer with a paddle attachment.
In a medium bowl sift all dry ingredients.
Alternating between the dry ingredients and the sour cream add to the mixer under medium speed until combined.
Add the lemon juice until fully incorporated.
In a separate mixing bowl, using a whisk attachment on your mixer, whisk the egg white until firm peaks form. You should be able to dip a spoon in and the egg whites peaks should stand without folding over.
Using a rubber spatula, fold in egg whites into creamed mixture. Do it enough to fully incorporate and then stop. Do not over mix.
Grease and coat with flour a 10" tube pan.
Add the mixture to the pan.
bake for 1 1/2 hours. The top should be golden brown and a toothpick should be free a cake batter if inserted and removed.