Roasted Tomato Salsa

In a small bowl, soak the onion in the lime juice for 15 minutes. In a dry, heavy-duty skillet (preferably cast iron) over high heat, "roast" the tomatoes, chile halves, and garlic clove until charred on all sides, about 2 to 5 minutes for the garlic, 8 to 10 minutes for the chiles, and 12 to 15 minutes for the tomatoes. Pulse in a blender; the mixture should remain slightly chunky. Transfer to a serving bowl and add the onion, lime juice, cilantro, and salt. Taste and add more salt or lime juice if needed. Use immediately or cover and refrigerate for up to a week.