01 - Preheat oven to 350°F. Grease and flour a 9×13-inch cake pan or line it with parchment paper.
02 - In a medium bowl, whisk together the 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 well combined.
04 - Add the eggs one at a time, mixing thoroughly after each addition. Stir in the vanilla extract.
05 - Fold in the mashed bananas and buttermilk (or yogurt) until just combined.
06 - Add the dry ingredients to the wet mixture, mixing gently just until no flour spots remain. Do not overmix.
07 - If using, fold in the chopped nuts or chocolate chips until evenly distributed throughout the batter.
08 - Pour the batter into the prepared pan and smooth the top with a rubber spatula.
09 - Bake for 35–40 minutes, or until a toothpick inserted in the center comes out clean.
10 - Allow the cake to cool in the pan for 15 minutes, then turn out onto a wire rack to cool completely. Serve plain or with your favorite frosting.