How to cook
In a small bowl, place the hard cold butter with the brown sugar, cinnamon and 0.5 oz (15 g) of flour. Rub the mixture with your fingers until it's crumbly and put it in the refrigerator.
In a blender, blend the bananas with the sugar and lemon juice into a puree. Beat the egg, add the butter and blend for a few seconds again. You can also beat it by hand, by mashing your bananas beforehand.
Sift the flour with the baking powder, baking soda and salt. Pour the mixture in portions to the liquid mixture and stir with a spatula until it is completely absorbed. In case you continue to work with the blender, pour the flour at once and blend briefly.
Distribute the banana mixture in 12 paper muffin forms, which are then placed in a special muffin tin.
Fill 3/4 of the volume of the muffins forms, so that they have room to rise.
Sprinkle each of the banana muffins with the cinnamon butter crumbs and put them in a preheated oven at 360°F (180 degrees) for 15-20 minutes.
Enjoy these fluffy banana muffins!