No-Peel Slow-Cooker Marinara Sauce

Cut tomatoes in half crosswise. Gently squeeze out the seeds and discard (don't worry if you don't get them all). Mix onion, oil, tomato paste, garlic, oregano, vinegar, sugar and 1 teaspoon salt in a 6-quart or larger slow cooker. Place the tomatoes on top.

Cover and cook for 2 hours on High or 4 hours on Low.

Puree with an immersion blender or in a regular blender in batches until chunky. (Use caution when pureeing hot liquids.) Placing the lid askew, cook until thickened, about 3 hours more on High or 6 hours more on Low.

Season with the remaining 1/2 teaspoon salt and pepper (or crushed red pepper) to taste. Puree further, if desired. Serve hot or let cool completely before refrigerating for up to 5 days or freezing for up to 6 months.