Roast the hazelnut kernels dry in a pan. Let cool a little and chop.
Scald buckwheat with boiling water, stir and put in a colander. Rinse under running water and drain. Bring the orange juice to the boil with 15 grams of brown sugar, add the buckwheat and simmer closed for about 15 minutes.
Wash the apples, quarter them and remove the core. Coarsely grate with the peel. Mix some lemon juice, the cranberries and 3/4 teaspoon cinnamon into the apples.
Grease a baking dish with a little butter and pour in the buckwheat up to 1 tablespoon. Layer the apple mixture on top.
Set aside 2 tablespoons of the chopped hazelnuts. Mix together the soft butter, cream, remaining hazelnuts, cinnamon and brown sugar and spread on the apple mixture. Scatter the rest of the buckwheat and hazelnuts on top.
Bake in the preheated oven at 200 degrees top / bottom heat or 180 degrees convection on the middle shelf for 30 minutes. Enjoy warm.