Preheat the oven to 350°F (175°C) and prepare the baking pan with parchment paper.

Whisk together the milk and lemon juice in a small bowl and let it sit for 5 minutes.

Blend rolled oats in a blender until fine flour consistency is achieved.

In a large bowl, whisk together oat flour, baking powder, baking soda, salt, and cinnamon.

Cream the butter and coconut sugar with an electric mixer until light and fluffy for 3-4 minutes.

Mix in eggs, maple syrup, and vanilla extract until combined.

Gradually add dry ingredients and soured milk alternately to the wet mixture, mixing gently.

Fold in the mashed bananas until just combined.

Pour the batter into the prepared baking pan and bake for 45 minutes or until a toothpick comes out clean.

Allow the cake to cool in the pan for 10 minutes before transferring to a cooling rack for at least one hour.