Preheat the oven to 200 degrees circulating air. Wash and peel the rhubarb, cut into bite-sized pieces and place in a baking dish. Squeeze the orange, mix the juice and 20 g sugar with the rhubarb.

Knead 2,130 g of softened butter, 140 g of sugar, 140 g of flour, cinnamon to taste (about half a teaspoon) and oat flakes to make crumble and spread over the rhubarb.

Bake the crumble for about 40 minutes. Delicious, also goes well with other fruits, e.g. plums, cherries ...