Set your oven to broil and move a rack to the top position.
Peel and quarter the onions, peel the garlic, and wash the tomatoes. Toss the tomatoes, onions, peppers, and garlic in olive oil, then spread everything out on a rimmed baking sheet. Don't peel the tomatoes.
Place the baking sheet under the broiler for about five minutes, then shake the baking sheet to rotate and flip everything. Broil a little longer to get all sides - and until the veggies are as charred as you would like.
Remove the baking sheet from the oven and allow the veggies to cool slightly. The tomatoes will burst with really hot liquid if you don't allow them to cool.
Slice open the jalapeños and remove the seeds and membranes. Add them to a food processor (or blender) with the onions and garlic, then lightly chop them.
Then add the tomatoes, cumin, lime juice, oregano, and cilantro and blend until smooth.
½ cup fresh cilantro, 1 lime, ¼ teaspoon ground cumin, 1 pinch dried oregano, 2 cups cherry tomatoes
Transfer the salsa to an airtight container. For the best flavor, allow the salsa to sit in the fridge for at least an hour, but 2-3 hours will allow the flavor to develop the most.
Taste the salsa, then add the salt, cayenne, and black pepper. Stir and taste the salsa again. Adjust the seasoning as needed - depending on the sweetness or tartness of the tomatoes, I've found that I sometimes have to adjust the lime, salt, or pepper to balance it out.
Serve the salsa with tortilla chips, tacos, or nachos.
Notes
Recipe yields 2 cups of salsa.
Storage
Store leftover salsa in an airtight container in the fridge. Be sure to use it up within 3-5 days.
Variations
If you want to make a spicy salsa, add an extra jalapeno or vice versa to make a mild salsa.
If you want to make a garlic-forward salsa, increase the amount of garlic cloves.
Roasting brings out the sweetness of the tomatoes and charring adds a fire-roasted flavor, so you can choose to lightly roast or char the tomatoes as much as you would like.