Preheat the oven to 350 degrees F. Grease a 9x13 baking pan and set aside.
In a medium bowl, whisk together flour, baking powder, baking soda, salt, and cinnamon. Set aside.
In another large mixing bowl, whisk together the melted butter and sugar until combined. Add the eggs and vanilla extract and beat until well combined. Stir in the milk. Fold in the mashed bananas, scraping down the bottom and sides of the bowl as necessary.
Gradually add in the flour mixture and mix until just combined - do not overmix, the batter will still be a bit lumpy.
Transfer the batter to the prepared pan and spread evenly. Bake at 350 F for 35-45 minutes. The cake is done when a toothpick inserted in the center comes out with little to no crumbs. Place the pan on a wire rack and allow the cake to cool completely before frosting.
For the frosting, beat cream cheese and butter together on high speed until smooth and creamy, about 3 minutes. Add confectioners' sugar and salt, then mix until medium speed until combined. Add vanilla and 1 tablespoon of heavy cream. Mix until combined and fluffy, scraping down bottom and sides of the bowl as necessary. Taste and add more sugar if you like it sweeter, and add 1 additional tablespoon of cream if a fluffier frosting is desired.
Transfer frosting to cooled cake and spread evenly. Garnish with ground cinnamon and chopped pecans if desired, then slice and serve.