Preheat the oven to 475 F, line a full-size sheet pan with foil and set aside.
Halve the tomatoes and tomatillos and place them on the pan. Slice the onions into 1/4″ slices, and spread on the pan.
Halve the peppers (remove the flesh and seeds if desired). Place on the pan. Sprinkle the garlic all over along with the salt and pepper. Roast for 20-25 minutes or until the peppers have charred slightly and the veggies are soft.
Remove from the oven and if needed, transfer half of the veggies into a blender along with half of the cilantro and lime juice. Place a cover loosely ensuring that it is vented to allow steam to release and process to desired consistency. If needed, repeat and blend the 2 batches together.
Place in containers and serve. Store any leftovers in the fridge for up to 2 weeks.
Notes
This will make ~8 cups of salsa. This depends on how much your process it.