Cook macaroni in boiling salted water according to package instructions, drain and sprinkle with approx. 1 tablespoon of oil. Whisk eggs and milk, season with salt, pepper and nutmeg. Cut ham into strips.
Grease the casserole dish (20 cm Ø). Alternate layers of macaroni, peas and ham strips. Pour the egg milk over it. Grate cheese coarsely. Spread the cheese, breadcrumbs and butter in flakes on the casserole.
Bake the casserole in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 1 hour. For the sauce, peel and chop the onions. Heat 1 tablespoon of oil in a saucepan. Fry the onions in it until transparent.
Stir in tomato paste. Add strained tomatoes, bring to the boil. Season with salt, pepper and sugar. Serve to the casserole. Wash the parsley, dab dry and chop finely, except for a little garnish.
Wash, clean and slice the tomatoes. Serve the casserole with tomato slices and parsley.