From Jane Brody’s Good Food Book

2 – teaspoons olive oil
1 – teaspoon butter or margarine
3 – cups thinly sliced onions (about 4 medium)
4 – cloves garlic, crushed or finely minced
1 – 35 ounce can tomatoes, drained well and diced, or 2 poinds fresh tomatoes, peeled, seeded, drained, and diced
1/2 – teaspoon salt, if desired, divided
Freshly ground black pepper to taste
2 – tablespoons minced fresh parsley or  teaspoons dried parsley flakes
1/2 – teaspoon dried basil
1/4 – teaspoon oregano
2 1/2 – pounds raw potatoes
1 – cup shredded Swiss cheese (4 ounces), divided
2 – tablespoons grated Parmesan, divided

1. Heat the oil and the butter or margarine in a medium skillet.  Add the onions and garlic, and saute them, stirring, for 1 minute.  Cover the skillet, and cook the vegetables over moderately low heat for a few minutes longer or until the onions are soft but not brown (do not let the garlic burn).

2. Remove the skillet from the heat, and add the tomatoes, 1/4 teaspoon of the salt, pepper, parsley, basil, and the oregano.  Mix the ingredients gently to combine them well.

3. Preheat the oven  to 325 degrees.

4. Peel and slice the potatoes very thin.

5.  To assemble the casserole, place one-third of the onion-tomato mixture in the bottom of a greased 3-quart casserole.  Spread one-half of the potatoes on top.  Sprinkle them with half the remaining salt (1/8 teaspoon), if desired, and some pepper.  Sprinkle one-half of the  Swiss cheese and 1 tablespoon of the Parmesan on the potatoes.  Repeat the layers:  another third  of the onion-tomato mixture, the rest of the potatoes, salt and pepper, and the remaining Swiss cheese and Parmesan.  Top the casserole with the remaining onion-tomato mixture.

6. Bake the casserole, covered, in the preheated oven for 1 hour 15 minutes.  Uncover the casserole, and bake 45 minutes longer or until the potatoes are tender but not mushy.