Mash the banana and prepare the blueberries.
Combine oat flour, baking powder, and salt in a bowl and mix well.
In another bowl, mix the mashed banana, egg, almond milk, and olive oil until well combined.
Add the wet ingredients to the dry ingredients and mix evenly.
Gently fold the blueberries into the batter.
Pour the batter into a mold and bake in a preheated oven at 180°C for 30 minutes.