Transfer the oatmeal to a bowl and cover with boiling water. Stir and let sit for 5-10 minutes, until the flakes swell and absorb all the water.
Peel the apple and cut it into small cubes. Remove pits from cherries. If using frozen cherries, defrost and drain the liquid beforehand. Add chopped apple and cherries to steamed oatmeal.
Also, add the egg and sugar.
Toss the oatmeal with the added additives.
Place the oatmeal mixture in a greased baking dish, flatten the surface, sprinkle with cinnamon and walnuts.
Bake the oatmeal in an oven preheated to 180 degrees for 30 minutes.
The baked oatmeal is ready! It can be served both hot and already cooled down. In the latter case, it is perfectly cut into portioned pieces.