1 tablespoon cinnamon sugar, for dusting the pan (I mixed 1 Tbsp sugar & 1/2 tsp cinnamon and used that)
1 package (15 ounces) yellow gluten-free cake mix
1/4 cup granulated sugar
1 heaping cup mashed bananas (about 3 small very ripe bananas)
8 tablespoons (1 stick) unsalted butter, melted (I used margarine)
3 large eggs
2 teaspoons vanilla extract
1 teaspoon ground cinnamon
3 tablespoons butter
3 tablespoons lightly packed light brown sugar
3 tablespoons granulated sugar
3 tablespoons heavy (whipping) cream
1/2 teaspoon pure vanilla extract
Banana Bread Cake
Place a rack in the center of the oven and preheat the oven to 350 degrees F. Lightly mist a 12-cup Bundt pan with vegetable oil spray, then dust it with the cinnamon sugar. Shake out the excess cinnamon sugar and set the pan aside.
Place the cake mix, sugar, mashed bananas, melted butter, eggs, vanilla, and cinnamon in a large mixing bowl and beat with an electric mixer on low speed until the ingredients are just incorporated, 30 seconds. Stop the machine and scrape down the sides of the bowl with a rubber spatula. Increase the mixer speed to medium and beat the batter until smooth, 1 1/2 to 2 minutes longer, scraping down the sides of the bowl again if needed. Pour the batter into the prepared Bundt pan, smoothing the top with the rubber spatula, and place the pan in the oven.
Bake the cake until it is golden brown and the top springs back when lightly pressed with a finger, 38-42 minutes. Transfer the Bundt pan to a wire rack and let the cake cool for 10 minutes. Run a long, sharp knife around the edge of the cake, shake the pan gently, and invert the cake onto a wire rack to cool completely, 30 minutes longer.
Meanwhile, make the Caramel Glaze.
Transfer the cake to a serving plate. Pour the glaze over the cake and let the glaze set for 15 to 20 minutes before slicing and serving the cake.
Place the butter, brown sugar, granulated sugar, and cream in a medium-size saucepan over medium heat and let come to a boil, stirring. Let the butter mixture boil for 1 minute, stirring constantly. Remove the pan from the heat and stir in the vanilla. Pour the glaze over the cooled cake.