Place the tomatillos and onion in a medium pot, cover with water, and bring to a simmer. Cook for 10 minutes, until the tomatillos are softened.
Drain, reserving a ¼ cup of cooking water and place in a blender, Add the reserved water, hot peppers, garlic, cilantro, and salt. Puree to a smooth consistency.
Place the oil in the pot and add the puree. Cook over medium heat for 8 minutes, stirring frequently, until all of the oil is combined.
Taste and adjust salt. Add lime juice for a more tart salsa.
Recipe by The Gardener Cook at https://www.thegardenercook.com/mexican-salsa-verde/