Preheat the oven to 450. Line a rimmed baking sheet with aluminum foil and set aside.

In a large bowl, toss the tomatoes, peppers and garlic with the oil, salt and pepper. Transfer the oiled vegetables to the prepared baking sheet and spread them into a single layer.  Bury the garlic cloves in the tomato halves to prevent them from burning.

Roast the vegetables for 20 minutes. Remove once the peppers have started to blacken and the tomatoes have begun to collapse.  Allow all of the vegetables to then cool slightly.

Transfer the slightly cooled vegetables to a food processor, fitted with a metal blade. Add the cumin, cilantro, red onion and  lime juice. Pulse about a dozen times, to achieve the texture of a chunky puree ( a dozen times was perfect for me). If the salsa is too thick, add more lime juice. Salt to taste (be generous!). Refrigerate at least 1 hour before serving.  These flavors need a little time to marry together.