Meanwhile, cut the onions into rings. Peel the apples and cut into 0.5-1 cm thick slices. Fry these in a coated pan. Take a little more margarine - it will bind afterwards. When the apple slices have lost the liquid and are slowly roasting, add the onion rings and fry both well. The onions should definitely not be limp. Means the mass can be dark.
Place the bratwurst on the plate, mashed potatoes and the fried onions and apples on top of the puree.