Remove the stems and seeds from the chiles using gloves and kitchen scissors.
3 Guajillo chiles
Place the dried chiles in a bowl, and pour enough boiling water over them to cover them completely. Let soak for 20-30 minutes, until soft.
Pour the chiles through a strainer with a cheesecloth, reserving the liquid. Then remove the cheesecloth and rinse the chiles thoroughly.
Add the chiles, 1 cup of the liquid, the lime juice, cilantro, garlic, and salt to a blender and blend until smooth.
4 cloves Garlic, 4 sprigs Cilantro, 3 Tablespoons Lime juice, 1 teaspoon Sea salt
Place the steak in a sturdy plastic bag, then pour in the marinade. Squeeze until it's well covered, then place in the fridge to marinate for 5 hours, or preferably overnight.
1 lb Flank steak
Remove the steak from the fridge and let come to room temperature, about 20 minutes. Add the oil to a cast iron pan, and heat over high heat until very hot. Then add the steak to the pan and sear, 3 minutes per side or until well browned.
2 Tablespoons Avocado oil
Continue cooking until the internal temperature reads 130°F, or 5 degrees below your target temperature. Remove, then place on a cutting board covered in foil and let rest for 10 minutes.
Slice thinly against the grain, then serve with your favorite sides and enjoy!