Directions:
1. Preheat oven to 425°F.
2. In a large oven-safe pot (like a dutch oven) toss together tomatoes, onion, chili pepper, garlic, olive oil, salt and pepper. Try to have as many tomato pieces with the skin facing upwards as possible.
3. Place the pot in the oven for 30 minutes. Remove and sprinkle the basil leaves on top. Put back in the oven and continue cooking for an additional 10-15 minutes. Remove when the tomato skins start to darken, the sauce is bubbling and the basil leaves have started to char.
4. Using a hand blender (or food processor/blender), blend the sauce for 10-20 seconds or until thickened with the desired consistency.
5. Stir in red wine vinegar.
6. Use in a recipe or split the batch in two and freeze in large mason jars for up to 3 months.