For the cake:
Preheat an oven to 350°F (177°C) Grease a 9x13 pan.
In a bowl, whisk together the flour, baking powder, baking soda, cinnamon, and salt. 3 cups (360 g) all-purpose flour 1 Tablespoon baking powder 1 teaspoon baking soda ½ teaspoon salt 1 teaspoon cinnamon
In a second bowl with a whisk together the melted butter, granulated sugar and brown sugar. ½ cup (99 g) granulated sugar ½ cup (107 g) packed light brown sugar 16 tablespoons (2 sticks, 226 g) unsalted butter
Add the eggs one at a time, mixing well after each addition, then mix in the vanilla and bananas. 4 large eggs 2 teaspoons vanilla extract 4 ripe medium bananas mashed (about 1 1/2 cups)
Add the flour mixture in 3 additions, alternating with the sour cream in 2 additions, mixing until just combined; scrape down the sides of the bowl as needed. Whisk until no traces of flour remain, about 30 seconds; do not overmix. 1 cup (227 g) sourcream
Pour the batter into the prepared pan and smooth the top. Bake in the preheated oven on a center rack for about 45 minutes until a toothpick inserted comes out with just a few moist crumbs.
For the cream cheese frosting
Combine the butter and cream cheese in the bowl of your stand mixer. 8 ounces cream cheese 8 Tablespoons (1 stick, 113 g) unsalted butter
Add the powdered sugar, one cup at a time. Mix on low until combined. 4 cups (452 g) powdered sugar
Add vanilla and mix until combined 2 teaspoons vanilla extract
Mix on medium sped until smooth and creamy.