1 2/3 cups all-purpose flour
1 1/2 cups granulated sugar
1 1/4 cups mashed very ripe bananas (3 large)
150 g butter
1 cup finely chopped nuts/raisins
1/2 cup buttermilk (or yoghurt or milk+Tbs vinegar-same ratio)
1 1/2 teaspoons baking powder
2 teaspoons baking soda
1/2 teaspoon salt
Heat oven to 175C. Grease and flour 13×9-inch pan or two 9-inch round cake pans. In large bowl, beat all cake ingredients with electric mixer on low speed 30 seconds, scraping bowl constantly. Beat on high speed 3 minutes, scraping bowl occasionally. Pour into pan(s).
Bake rectangle 45 to 50 minutes, rounds 35 to 40 minutes, or until toothpick inserted in center comes out clean. Cool rectangle in pan on cooling rack. Cool rounds 10 minutes; remove from pans to cooling racks. Cool completely, about 1 hour.