This cake is moist and very tasty. The frosting is delicious.
Preheat the oven to 320°.
Grease and line two 9 inch cake pans with parchment paper and set aside.
Cream the butter and sugar until light and fluffy.
Add egg yolks, one at a time, mixing after each one.
Add the flour, baking powder, salt, and baking soda and mix until mostly combined.
Add the yogurt and mix until combined.
Beat the egg whites to medium peaks and fold into the cake batter, fold in the raspberries (or blueberries).
Divide the batter evenly between the two pans and bake for 18-24 minutes.
Start checking at 15 minutes, you will need to keep an eye on it so it does not overbake.
Let the cakes cool in the pan for about 10 minutes before turning them out on wire rack to cool completely before icing.
Chef's notes: Separate eggs before you bring them to room temperature. They are easier to separate cold. The original recipe for this cake called for 6 inch cake pans. I converted it to 9 inch cake pans, and adjusted the baking time. You will need to keep an eye on it and check it at 15 minutes, then every 5 minutes until done. Don't overbake.