Preheat the oven to 350ºF. Grease the muffin tin with non-stick cooking spray or line with 12 paper liners.
In a bowl, combine flour, quick-cooking oats, brown sugar, granulated sugar, baking powder, baking soda, cinnamon, cardamom, and salt. Set aside.
In another large mixing bowl, whisk together mashed bananas, eggs, melted butter, and vanilla extract until combined. Add the dry ingredients. Stir using a rubber spatula until just combined. Do not overmix the batter.
Divide batter between the 12 prepared muffin tins. Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean, and they are golden on top and springy to the touch. Remove from the oven. Let the muffins cool slightly inside the muffin tins. Then, transfer to a cooling rack. Enjoy!