So I'm making a surprise birthday cake for my friend who loves peanut butter but the thing is the cake is so dense it's like a banana bread! Do you guys have any suggestions on how to lighten it? here's the recipe:

3 cups unbleached all-purpose flour

• 2 cups white sugar

• 1 teaspoon salt

• 1 teaspoon baking powder

• 1/2 teaspoon baking soda

• 1 cup buttermilk

• 1 cup butter

• 2 teaspoons vanilla extract

• 4 eggs

• 1 cup peanut butter

bake for 60 mins for 325 F

Beat the egg whites separately and fold them in at the end.