2. Add the tomatoes, sugar, salt and pepper and simmer for 10 minutes.
3. Puree the sauce in a blender or food processor. (The sauce may be made in advance and stored in the refrigerator for up to 3 days.)
For the enchiladas:
1. In a large skillet, heat the oil over high heat. Season the steak with salt and pepper and brown it in the hot pan. Transfer the steak to a plate and set aside.
2. Using the same skillet, reduce the heat to medium and add the onion and garlic. Cook for 2 minutes.
3. Add the potato, tomato, oregano, cumin, salt and pepper and cook for 10 minutes. Add the steak, raisins and olives and stir to combine.
4. Preheat the oven to 350ºF.
5. Fill the corn tortillas with the steak mixture and arrange them in a single layer in a large baking dish. Cover the enchiladas with the sauce and sprinkle with cheese.
6. Cover the baking dish with foil and bake for 20 to 25 minutes. (This may be made in advance, stored in the refrigerator for up to 3 days and heated before serving.)