Prep time: 15 minutes
Total time: 1 hour 45 minutes
2 pounds|1 kg plum tomatoes, seeds removed and roughly chopped
2 yellow onions, 1 finely chopped, 1 thinly sliced into rounds
5 tablespoons|75 ml olive oil
2 pounds|1 kg Idaho potatoes, peeled and thinly sliced into 1/4-inch thick rounds
1 ½ pounds|680 grams provolone cheese, finely diced
1. Heat the oven to 400°F. In a medium skillet, heat 3 tablespoons of the olive oil over medium-high. Add the diced onion and cook until soft, 3 minutes. Stir in the tomatoes, salt, and pepper and cook until soft but still chunky, 6 minutes. Remove from heat.
2. Drizzle 1 tablespoon olive oil in the bottom of a 7-inch-by-11-inch casserole dish. Spread a thin layer of tomato sauce on the bottom, followed by a layer of potatoes. Sprinkle with salt and pepper. Top with the thinly sliced onions and sprinkle on some oregano and provolone. Continue layering, finishing with a layer of cheese. Drizzle on any remaining tomato sauce. You should have about 3 layers of potatoes.
3. Cover with aluminum foil and bake for about 1 hour. Uncover and cook until the cheese is melted and golden, 25 minutes longer.