In a large bowl, toss the tomatoes in a drizzle of any high smoke point oil. Grab your peppers and onion, and walk them out to the grill. (You can also use an indoor grill pan or a cast iron skillet for this step. I’ve also had good results just charring the onion and jalapeno straight over a gas burner.)
Toss the oiled tomatoes, peppers and onion onto the grill. The goal is for the skin of the peppers and the edges of the onion to get some char, for the tomato skin to get blistered enough that you can peel it off, and for the raw edge to get taken off of most of the tomato. Don’t let it get overcooked and mushy, though.
Remove the tomato, peppers, and onion from the grill. Put the tomatoes back in the same bowl you used to toss them in. Cover the bowl with a plate to let the tomatoes steam. This will help remove the skin. Use the blade of a knife to scrape the skins off of the peppers, and remove seeds as desired (we do not remove them).
Transfer the peppers to the bowl of a food processor along with the onion, garlic, and cilantro. Pulse a few times until coarsely chopped.
Using your fingers, peel the tomatoes. The skin should come off easily. If you can't get every last bit of skin, don’t worry. Add the tomatoes to the food processor, along with the white vinegar, salt, and liquid smoke. Pulse until you reach your desired consistency (from chunky to runny).
Pour the salsa into a resealable container and transfer to the refrigerator. The salsa is best served chilled, so let it sit for at least 1 hour in the refrigerator, or ideally overnight, before serving.
NOTE: You can use all serranos or all jalapenos for a recommended minimum of 2, but ideally, use 2 of each for a moderate-yet-keeping-it-interesting level of spice).