Preheat the oven to 350°F.

Line a 12-cup and a 6-cup cupcake pan with paper liners and set aside.

Place the bananas, butter, brown sugar, granulated sugar, and vanilla in a large mixing bowl. Using a hand mixer or a stand mixer fitted with a whisk attachment, cream the ingredients together on medium speed until smooth, about 1 minute. Add the sour cream and eggs, and continue to beat until the mixture is light and fluffy, about 1 minute.

Sift the flour, cinnamon, baking powder, baking soda, and salt into the bowl. Beat the mixture on low until the ingredients begin to come together. Slowly pour in the buttermilk and continue mixing, scraping down the sides of the bowl with a rubber spatula as needed, until a smooth, medium-thick batter forms.

Divide the batter evenly among the cupcake liners, filling each about two-thirds full.

Bake the cupcakes on middle rack of oven until a toothpick inserted in the center comes out clean, 18-21 minutes.

Check to see that cupcakes are done. Remove from oven or add time as needed.

Allow the cupcakes to cool completely to room temperature before frosting.

While the cupcakes cool, make the frosting. Place the cream cheese and butter in a large mixing bowl. Beat with a hand mixer on medium speed until smooth and creamy.

Add the powdered sugar in two additions, beating on low speed after each, until the sugar is fully incorporated into the cream cheese mixture. Add the vanilla extract and salt. Continue beating on medium-high speed until the frosting is light and fluffy, 2-3 minutes.

Pipe or spread the frosting onto the cooled cupcakes. Refrigerate until ready to serve.