For this recipe, I combined both raw and roasted veggies. I think it gives you a great balance of the roasted and fresh flavors, which are both so good in peppers and tomatillos. (But, if you are short on time, you can make your tomatillo salsa with simply raw, fresh veggies, or even buy your favorite store-bought tomatillo salsa.)
If you want the roasted-raw hybrid tomatillo salsa, preheat the broiler to high and take 8 of the tomatillos, 1 serrano chili, 1 jalapeño pepper and half of the chopped onion and place on a baking sheet. Place approximately 4-5 inches under the broiler and broil for about 4 minutes per side, or until dark blisters start to form on the skins. Remove from oven and allow to cool.
Meanwhile, rinse the remaining chopped onion in cold water for a couple of minutes and then squeeze the water out. This softens the potency of the raw onion.
Coarsely chop the remaining raw tomatillos, chilis and peppers and place them in the food processor along with the rinsed, chopped onion, garlic and cilantro leaves. Process until desired chunkiness.
Add the cooled roasted veggies and continue to process. Stir in lime juice, olive oil and salt. Can be made several days ahead of time. Store in airtight container and refrigerate until ready to use.