Set oven to broil.
Place tomatillo, red onion, garlic and serrano on a baking sheet. Broil for 15 minutes in the oven, flipping over the ingredients half way. After roasting the tomatillo should be soft. If the red onion is still a little solid, toss it back in the oven for an additional 5 – 10 minutes, careful not to let it burn.
Peel the garlic.
Set the desired amount of heat by removing some or ALL of the seeds from the serrano pepper (and removing the stem).
Place the roasted ingredients in a food processor, then add cilantro, olive oil, lime, sea salt & pepper and liquid smoke.
Pulse blend but careful not to overdo it. You want it somewhat chunky.