Preheat your oven to 350°F (175°C). In a mixing bowl, prepare the cake mix according to the package instructions, adding in the mashed ripe bananas. Pour the batter into a greased 9x13-inch baking pan and bake for 25-30 minutes until golden brown.

While the cake cools, whisk together the evaporated milk, sweetened condensed milk, whole milk, and cinnamon until smooth. Set the mixture aside.

Once the cake is cooled, poke holes all over the surface with a skewer or fork. Gradually pour the tres leches mixture over the cake, covering every corner. Allow the cake to absorb the mixture for 15-20 minutes.

Cover the cake with plastic wrap and refrigerate for at least 4 hours, preferably overnight.

Before serving, whip the heavy cream until soft peaks form. Spread or pipe over the chilled cake and sprinkle with chopped pecans. Serve chilled or at room temperature.