Top a sheet pan with red bell peppers, olive oil, salt, pepper, and chili flakes. Add tomatoes, garlic, and onions. It makes no difference how you cut the food; ultimately it will all be puréed. I kept the garlic's skin on so it wouldn't burn or become too brown and sliced everything down really small.
Sear at 425 degrees Fahrenheit for 35 to 45 minutes. The bell peppers will burn, the garlic will get extremely soft and delicious, and the onions and tomatoes will get rather little. Ten minutes will fly while the vegetables cool
Whirl the vegetables in a blender or food processor once they have cooled. Put the tray into the saucepan you will use for stewing later and combine it with an immersion blender for even less work. Add all the still-present liquids, but be sure the garlic isn't in its peel
Blend until the desired texture is acquired. Put the mix in a pot if it isn't already there and toss the chopped basil, salt, and chili flakes. Start with two tsp of salt and add either more or less based on taste
Cook the sauce gently for five to seven minutes, covered on low heat. You may now can it, store it in a jar sealed tightly against air, or consume it straight away with pasta or crusty bread