In a large bowl, whisk together the flour, baking powder, salt and cinnamon.

Set aside. In a separate large bowl, mix together with a wooden spoon the vegetable oil, brown sugar, eggs, milk and sour cream until well incorporated.

Add in the mashed banana until well combined.

Gently fold in the dry ingredient mixture until no dry spots of flour are left.

Fill each cup of muffin tin about ¼ of the way with muffin batter.

Place a teaspoon of dulce de leche on top of the batter.

With a toothpick, gently swirl the dulce de leche into the muffin batter.

Add more muffin batter on top until the muffins cups are ½ full.

Place another teaspoon of dulce de leche on top and swirl around with a toothpick gently.

Sprinkle tops with sparkling sugar.

Bake for 5 minutes, then lower the oven temperature down to 350 degrees F for another 15 minutes, or until a toothpick inserted into the center of the center muffin comes out clean.

Allow to cool in muffin tins for 10 minutes, then transfer to a wire rack to cool completely.