2 tablespoons butter
1 large onion, diced
2 cloves garlic, minced
2 tablespoons tomato paste
1 32-ounce can whole, peeled San Marzano tomatoes
1 teaspoon salt
1/4 teaspoon black pepper
1/4 teaspoon crushed red pepper
1 pound ricotta cheese
2 eggs
1/2 cup Parmesan cheese
1 tablespoon dried Italian seasoning
1 pound lasagna noodles
6 slices mozzarella cheese
6 slices Swiss cheese
Preheat the oven to 350 F.
Heat the butter in a heavy-bottomed pan over medium-low heat. Add the onion and cook, stirring occasionally, until tender, about 10 minutes.
Add the garlic and tomato paste, stir to combine, then add the tomatoes, salt, pepper and crushed red pepper. Simmer for 30 minutes, then use an immersion blender to purée.
Meanwhile, combine the ricotta, eggs, Parmesan and Italian seasoning in a bowl.
Cook the lasagna noodles in boiling water just until flexible. Set aside in a water bath.
Spread a layer of tomato sauce in the baking dish. Top with a layer of precooked lasagna noodles. Spread with about 1/3 of the ricotta mixture and 1/3 of the mozzarella. Top with 1/3 of the tomato sauce, and repeat. On the last layer, do not add the final third of the mozzarella.
Cover the lasagna with aluminum foil, and bake for 1 hour.
Remove the foil, add the reserved mozzarella, and continue baking for 1015 minutes, until bubbly and golden brown on top.
Allow to rest about 20 minutes before serving.