Preheat oven to 350 degrees. Grease and flour a 9"x13" pan. Set aside.

In a large mixing bowl, cream butter and sugar until light and fluffy. Add eggs and vanilla and blend thoroughly. Sift together flour , baking powder, baking soda and salt. Add to creamed mixture alternately with sour cream, beginning and ending with dry ingredients. Stir in bananas and pecans. Spread batter evenly over bottom of pan and bake 40 to 45 minutes. Cool and frost with Cream Cheese Frosting.

Cream Cheese Frosting: Combine all ingredients and blend well.