Preheat your oven to 350°F (175°C). This ensures that your muffins will bake evenly.
Lightly grease your muffin tin with coconut oil or use silicone liners to prevent sticking.
In a mixing bowl, combine the smashed bananas, melted coconut oil, and egg. Mix well until all ingredients are fully incorporated.
In another bowl, whisk together the all-purpose flour and baking soda. This will help distribute the baking soda evenly throughout the batter.
Gently fold the dry ingredients into the wet mixture, being careful not to overmix. The batter should be slightly lumpy.
Gently fold in the blueberries, ensuring they are evenly distributed throughout the batter.
Scoop the batter into the muffin tin, filling each cup about 3/4 full.
Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the muffins from the oven and let them cool in the tin for about 5 minutes before transferring them to a wire rack.