Remove the papery husks from the tomatillos, rinse off the sticky coating and halve or quarter them. Heat the oil in a skillet over medium-high heat. Add the tomatillos, diced onion, jalapeños and garlic. Cook for 3–5 minutes, turning occasionally, until lightly charred.
Remove from heat and let it cool down. Transfer to a blender jar with the cilantro.
Add lime juice and season with salt, pepper and ground cumin.
Blend for 1-2 minutes on high speed until no chunky bits are left.
Notes
Use firm, fresh tomatillos and remove their papery husks before rinsing off the sticky coating.
Pat the tomatillos dry after rinsing to help them char rather than steam in the skillet.
Cook the vegetables in a wide skillet over medium-high heat until lightly charred. Avoid burning the garlic, as it can make the sauce bitter.
Remove the seeds and white membranes from the jalapeños for a milder sauce, or replace one with a serrano pepper for extra heat.
Let the cooked vegetables cool slightly before blending with the cilantro, lime juice, and seasonings.
Add a splash of water while blending if the sauce is too thick, adjusting until it reaches your preferred consistency.
Use freshly squeezed lime juice and adjust the salt and pepper after blending for the best flavor.
Serve over enchiladas, tacos, burrito bowls, grilled chicken, or scrambled eggs.
Store leftovers in an airtight container in the refrigerator for up to 3 days, or freeze in individual portions for longer storage.