-Heat broiler, with rack in top position.
-Add the following in a single layer to a rimmed baking sheet.
2 large tomatoes
1 medium white onion, halved
3 garlic cloves, unpeeled
-Broil until vegetables are blistered and slightly softened, rotating sheet and flipping vegetables frequently, 6 to 8 minutes (garlic may need to be removed earlier if it is browning too quickly).
-Discard garlic skins.
-In a food processor, pulse garlic and vegetables until coarsely pureed.
-Add 3 TBS fresh lime juice, (the juice from 1-2 limes)
-Season with sea salt and freshly ground black pepper and pulse to combine.
-Transfer salsa to a bowl and stir in ¼ cup chopped cilantro.
-Serve warm or cold.