Preheat oven to 350°F (180°C). Line two 12-hole mini muffin trays with oil spray. Set them aside.
Peel, mash the bananas with a fork and measure 1 cup - precision is important to avoid gummy muffins.
Place the mashed bananas in the jug of a high-speed blender along with the remaining ingredients: coconut oil, milk, lemon juice, baking powder, baking soda, and rolled oats.
Blend on high-speed - speed 10 of my Vitamix - for 1 minute, stopping every 20 seconds if needed to scrape down the sides of the jug. Keep blending until the batter is smooth and no bites of oats are showing.
Fill the muffin holes with about 1-2 tablespoons of batter.
Bake in the center rack of the oven until golden brown, and a pick inserted in the center of the baby muffins comes out clean - about 12-15 minutes.
Cool them down immediately on a wire rack.
Serve plain or with fruits and yogurt on the side.