Cut the meat into small pieces and put in a baking dish, salt a little.
Cut the onion in half rings and put on the meat.
Cooking the sauce. Melt the butter in a pan, add the flour and stir well. Slowly pour milk, season to taste and cook until the sauce thickens constantly stirring.
Drizzle the meat with half the sauce.
Cut the mushrooms into slices, put into a mold, and tomatoes cut into half rings on them. Pour the rest of the sauce.
Sprinkle with cheese and bake in the oven at 180 degrees 50 minutes.
Pork with vegetables in bechamel sauce is ready, serve hot.