Preheat oven to 350°F (175°C). Grease a Bundt pan generously.
In a bowl, whisk together flour, baking soda, baking powder, salt, and cinnamon.
In another bowl, combine mashed bananas, melted butter, sugars, eggs, and vanilla.
Add sour cream and stir until smooth.
Gradually add dry ingredients, mixing just until combined.
Fold in nuts or chocolate chips if using.
Pour batter into prepared Bundt pan and smooth the top.
Bake for 45–50 minutes or until a toothpick comes out clean.
Cool in pan for 10 minutes, then transfer to a wire rack.
Once cool, whisk glaze ingredients and drizzle over the cake.