INGREDIENTS
1
box white cake mix
1/4 cup
oil
4
egg whites
3/4 cup
buttermilk
3/4 cup
sour cream
1
vanilla bean (or 1 tablespoon vanilla extract)
3
eggs
1 cup
sugar
1/2 cup
fresh lemon juice
1/4 cup
butter, melted
1 tbsp
lemon zest
1 cup
butter, softened
2 tbsp
mashed blueberries
4 cups
powdered sugar