Meyer Lemon Iced Raspberry Yogurt Cake

9 tablespoons unsalted butter, room temperature
1 cup sugar
3 eggs, separated
2 cups all purpose flour
1 tablespoon baking powder
1 teaspoon salt
1/2 teaspoon baking soda
1 cup plain greek yogurt
1 cup raspberries, fresh or frozen

for the buttercream:
8 ounces cream cheese, room temperature
8 tablespoons unsalted butter, room temperature
zest & juice of 2 meyer lemons
pinch of salt
4 cups powdered sugar

1. to make the cake, preheat your oven to 320F. grease and line four 6" cake pans or two 8" or 9" cake pans with parchment paper and set aside.
2. cream the butter and sugar until light and fluffy. add the egg yolks one at a time, mixing after each addition. 
3. add the flour, baking powder, salt, and baking soda and mix until mostly combined. add the yogurt and mix until combined. 
4. beat the egg whites to medium peaks and fold into the cake batter. fold in the raspberries.
5. divide the batter evenly between the pans and bake 25-30 minutes, or until a toothpick comes out clean. 
6. let the cakes cool in the pan for about 10 minutes before turning them out onto a wire rack to cool completely before icing.
7. to make the buttercream, cream the cream cheese and butter until smooth. add the lemon zest and juice and salt and mix until combined. slowly add the powdered sugar and mix until combined. mix on medium speed for a couple minutes until light and fluffy. if your buttercream is softer than you'd like, you can either add more sugar or chill it for 30 minutes.
8. to make a four layer cake, slice each cake layer in half. spread with buttercream and top with another cake layer. continue until all layers are used. spread the cake with remaining buttercream. store finished cake in the refrigerator.