01 - Preheat oven to 350°F. Grease and flour a 9-inch round or square cake pan, then line the bottom with parchment paper for easy release.
02 - In a large mixing bowl, beat together the mashed bananas, vegetable oil, granulated sugar, eggs, and vanilla extract until smooth and well incorporated.
03 - In a separate bowl, whisk together the all-purpose flour, baking soda, baking powder, salt, and ground cinnamon until evenly distributed.
04 - Gradually add the dry ingredient mixture into the wet ingredients, folding gently with a spatula until just combined. Stop mixing as soon as no dry streaks remain to keep the cake tender.
05 - If using, gently stir in the chopped walnuts or pecans and chocolate chips until evenly distributed throughout the batter.
06 - Pour the batter into the prepared cake pan and smooth the surface with a spatula to ensure even baking.
07 - Bake on the center rack for 35 to 40 minutes, or until a toothpick inserted into the center comes out clean and the top springs back lightly when touched.
08 - Allow the cake to cool in the pan for 10 minutes, then carefully invert onto a wire rack to cool completely before slicing and serving.