Preheat the oven to 250 degrees Celsius (475 degrees Fahrenheit)
On a baking sheet place the tomatoes, garlic cloves, slices of pepper, onion and the halved jalapeños. Drizzle with olive oil and sprinkle with salt.
Place the tray in the oven and bake for 5 minutes, make sure to keep an eye on it to ensure the garlic doesn't burn. After 5 minutes flip the veggies and cook for another 4-5 minutes.
Remove from the oven and allow to cool slightly. Toss everything into the food processor along with the cumin, lime juice and cilantro.Pulse until the veggies have broken down into a chunky texture. Taste and add more lime juice, salt or cumin as required.
The salsa will last in the fridge for 4 days.