Jenny's Mom's Banana Cake

I got this recipe years ago from the mother (Joan Phillips) of a former colleague of mine (Jenny Good). I went to stay at her house and she served this delicious banana cake. Though I've never seen the mother since, and have lost touch with the daughter years ago, this is still "Jenny's Mom's Banana Cake." I've never found a better recipe for banana cake.

2 1/4 C. flour (I use half whole wheat if it is freshly ground)
1 tsp. baking powder
3/4 tsp. baking soda
1/2 tsp. salt
1/4 lb. (1 stick) butter, softened
1 1/2 C. sugar
2 eggs
2-3 mashed bananas (she used only fresh, but I'll use over-ripe ones if I need to)
1/2 C. sour cream (be generous)
1 tsp. vanilla

Sift together first four ingredients and set aside.
Cream together butter and sugar.
Add eggs, beating after each addition.
In a separate bowl, cream together bananas, sour cream, and vanilla.
Finally, add flour mixture to butter mixture alternately with banana mixture.
Bake in 2 9" square greased-and-floured pans at 350 degrees for 30 minutes. (Unless I'm going for a serious special presentation, I use a 9 x 13 pan and make excess batter--there's not much--into muffins.)

Frost when completely cooled with butter cream frosting.