Use this classic recipe when making our Stuffed Eggplant Parmesan.
Spray a nonstick skillet with olive-oil spray, and place over low heat. Add onion and garlic; cover, and cook until translucent, about 7 minutes. Add tomatoes, salt, and pepper; bring to a boil. Lower heat to medium low; simmer 25 to 30 minutes. Pass sauce through the largest holes of a food mill, and set aside.