Preheat the oven to 350-degrees Fahrenheit. Spray a muffin pan with non-stick cooking spray or line with muffin papers.
In mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, ground cinnamon, and salt. Set aside.
In a large bowl, mash the ripe bananas using a fork. Add the brown sugar, vegetable or canola oil, egg, and vanilla extract. Blend until well combined.
Add the dry ingredients to the banana mixture. Stir just until combined.
Fold in the shredded carrots and the chopped nuts, if using.
Scoop the carrot banana muffin batter into the muffin tin filling each cup to about ⅔ full.
Bake the banana carrot muffins for 18 - 20 minutes, until a toothpick inserted into the center of one of the muffins comes out clean.
Let the muffins cool for about 5 minutes before removing them from the muffin pan. Place on a wire rack to cool completely.
Notes
Store your muffins in an airtight container at room temperature for up to 3 days, or freeze them for up to 3 months. Just thaw at room temperature or warm them up in the microwave for a quick snack.VariationsIn place of the nuts, try raisins instead.Other than just cinnamon, try other warm spices such as nutmeg, ginger, or pumpkin pie spice.