Amazingly Easy Banana Cake Recipe With Cake Mix

For the Cake:

2 cups gluten-free baking flour
1 teaspoon baking powder
1 tablespoon cinnamon
1/2 teaspoon kosher salt
3 ripe bananas, mashed

1 cup sugar
1/2 cup unsalted butter, softened
2 large eggs
1 teaspoon vanilla extract