Fifteen Kilograms of Imperfect Lemons

Slice a large bunch of rhubarb into cubes. Put in pan with 15g butter, a tablespoon cornflower, 100g caster sugar and a tablespoon vanilla extract. Cook until butter and sugar have melted and sauce thick. Meanwhile, rub 120g butter with 150g plain flour, 90g sugar and a teaspoon baking powder until crumbly. Pour rhubarb into tarte tatin dish then sprinkle crumble on top and then bake for 35 minutes at 180°C.