In a bowl with an electric mixer, beat the peanut butter and butter together until smooth. Beat in eggs until completely blended. Then beat in the pureed bananas and the vanilla.
Combine all the dry ingredients. Add to the banana mixture a little at a time, beating until completely blended.
Pour batter into a nine-by-five-inch loaf pan. Bake in preheated 350-degree oven 50 minutes, or until a skewer inserted into the center comes out clean.
Cool 10 minutes in pan, then turn onto a wire rack to complete cooling.
