Position an oven rack 6 inches from the broiler and preheat the broiler to high.

Place the Roma tomatoes, jalapeños, onion quarters, and unpeeled garlic cloves on a rimmed baking sheet. Broil for 10-12 minutes, turning once halfway, until the tomato skins are blackened and blistered in spots and the onion edges are charred.

Remove the baking sheet from the oven. Transfer the garlic cloves to a small bowl to cool slightly. Let the remaining vegetables cool on the sheet for 5 minutes.

Once cool enough to handle, peel the garlic cloves and discard the skins. For the jalapeños, you can leave the stems on but remove the blackened skins if you prefer a milder salsa (the skins add bitterness). If you want less heat, slice the jalapeños open and scrape out the seeds and white ribs before adding to the blender.

Transfer the charred tomatoes, jalapeños, onion, and peeled garlic to a blender or food processor. Add the cilantro, lime juice, salt, and cumin.

Pulse 8-10 times for a chunky salsa, or blend continuously for 15-20 seconds for a smoother texture. Taste and adjust salt or lime juice as needed.

Transfer to a bowl and let rest for at least 15 minutes before serving to allow flavors to meld. Serve at room temperature or chilled.