Preheat the oven to 400°F (200°C).

Place the halved tomatoes, quartered onion, unpeeled garlic, and halved jalapeño on a baking sheet.

Drizzle with olive oil and sprinkle with salt and black pepper.

Roast in the preheated oven for about 25-30 minutes, or until the tomatoes are blistered and the onion is tender.

Remove the baking sheet from the oven and let the ingredients cool slightly.

Peel the garlic cloves and add all roasted ingredients to a blender or food processor.

Add lime juice and chopped cilantro, then blend until desired consistency is reached.

Taste and adjust seasoning if necessary.