Add the olive oil to a large pan and heat it through to medium-low.
Add the peppers, tomatoes, onion and garlic.
Season with salt and pepper and stir.
Cover and cook on medium-low for 30 minutes to 1 hour, depending on how softened you’d like your peperonata.
Adjust for salt and pepper, then garnish with basil (whole or chopped). Sprinkle with spicy chili flakes if you’d like a bit of extra flavor and heat.