First make the compote: Add fresh or frozen berries to a pan over medium heat. Add sweetener of choice and cook, stirring occasionally for 5-8 minutes.
If the compote looks too watery (if using frozen berries), cook over a high heat for a few minutes to get the right consistency. Set aside. The compote can be made up to a few days in advance and refrigerated. Reheat before serving.
Add the oats to a blender jar and blend to a fine flour. Add all the other ingredients (except butter) - baking powder, baking soda, salt, banana, egg, milk, and lemon juice. Blend again until combined.
Add a small knob of butter onto a non-stick pan. Pour about 1/4 cup of the batter per pancake. Wait for bubbles to appear on the top, then flip to cook the other side. Cook in batches.
Serve immediately with the compote.
Notes
I've used raspberries for the compote, but blueberries, blackberries, strawberries or a mix of them would all work.