pure vanilla extract
vanilla bean paste or extract
Cream sugar,sour cream egg and 2 tablespoons softened butter.
Add mashed bananas and 1 teaspoon vanilla extract.
Add flour salt and baking soda;mix well.
Pour into greased 8x8 pan.Bake at 375 for 20-25 min. until a toothpick inserted in the center comes out clean.
Cool completely before frosting.
Frosting: Cream butter and confectioners sugar together until smooth. Slowly add the heavy cream;stir until smooth. Stir in the vanilla bean paste or extract until fully incorporated. Spread on cake.