Wash and remove stems from the tomatoes. Wash and dry the peppers.
Peel the dry husks from the tomatillos, wash off the sticky residue and dry. Peel the onions and garlic (if using).
In a dry heavy skillet or cast-iron griddle over medium high heat, roast the chiles, tomatoes, garlic, onion and tomatillos in batches until they are dark brown and fragrant. Turn them with tongs to brown evenly. Do not add oil or salt or any other ingredient to the pan.
Also don't crowd the pan as the vegetables need space to develop the wonderful charring that's one of the keys to success in this salsa. This should take around 3 minutes per batch. As the vegetables brown, remove them and place in a bowl.
Once all the vegetables are charred, remove the blackened skins and the eye of the tomatoes. Don't worry about removing all of the browned parts as they do add to the flavour.
Squeeze the tomatoes one by one with your hands to extract as much moisture and seeds as possible. Chop them coarsely and place inside a 2 quart cooking pot.
Chop the onions, tomatillos, garlic and cilantro and place in the cooking pot.
Wipe the skins of the peppers to remove any thick skins. Then, remove stems and slit the peppers lengthwise and shake or brush out the seeds and pull out the veins.
Chop the sweet bell peppers coarsely and the hot peppers finely, adding them to the cooking pot.
Mix the vinegar, tomato paste, salt, cumin and oregano (if using) in a bowl. Pour into the tomato and tomatillo mixture and stir.
Bring to a boil slowly and cook, stirring often, for 10-15 minutes. Remove from the heat and serve at room temperature.
Store covered salsa in the refrigerator for up to 1 week or freeze.