Preheat your oven to 350°F (175°C) and grease or line a 9-inch round cake pan.
In a large mixing bowl, whisk together the mashed bananas, sugar, and vegetable oil until the mixture is smooth and fragrant.
Add the eggs to the banana mixture one at a time, whisking well after each addition to incorporate air and create a rich, velvety batter.
In a separate bowl, sift together the flour, baking soda, and cinnamon. Gradually fold these dry ingredients into the wet batter, mixing just until combined to keep the batter light.
Stir in the chopped walnuts, distributing them evenly throughout the batter for that delightful crunch in every bite.
Pour the batter into the prepared cake pan, smoothing the top with a spatula for an even surface.
Bake for about 50 minutes, or until a toothpick inserted into the center comes out clean. The cake will turn a golden brown and smell warmly of bananas and spices.
Allow the cake to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely. This helps set the crumb and makes slicing easier.
While the cake cools, whip the heavy cream with powdered sugar until soft peaks form, creating a light, fluffy topping.
Spread the whipped cream generously over the cooled cake or serve on the side for a creamy contrast to the nutty, caramelized flavors.
Slice and enjoy this rustic banana walnut cake, noting its moist crumb, crunchy walnuts, and creamy topping as you serve.
