01 - Preheat oven to 350°F. Grease and flour a 9x13-inch cake pan or line it with parchment paper.
02 - In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until evenly distributed.
03 - In a large bowl, beat together the granulated sugar and vegetable oil (or melted butter) until thoroughly combined.
04 - Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract until blended.
05 - Gently fold the mashed bananas and buttermilk (or yogurt) into the wet mixture until just combined.
06 - Add the dry ingredient mixture to the wet ingredients, folding gently just until no flour spots remain. Take care not to overmix.
07 - If using chopped nuts or chocolate chips, fold them into the batter at this stage.
08 - Pour the batter into the prepared cake pan and smooth the top with a rubber spatula for an even surface.
09 - Bake for 35 to 40 minutes, or until a toothpick inserted into the center comes out clean.
10 - Allow the cake to cool in the pan for 15 minutes, then turn it out onto a wire rack to cool completely. Serve plain or topped with your favorite frosting.