In a large bowl, mix eggs, sugar, sour cream, bananas, and vanilla until well blended. In another bowl, stir together flour, baking powder, baking soda, salt, cinnamon, ginger, and cloves. Stir flour mixture into banana mixture just until well blended. Scrape batter into a buttered and floured 9-inch square baking pan.
Bake in a 350° regular or convection oven until top springs back when gently pressed and a skewer inserted in the center comes out with moist crumbs attached, 30 to 35 minutes. Dust with powdered sugar before cutting into squares; serve warm or cool from pan.