Remove and discard stems and seeds from guajillo chiles, break chiles in half. Cover with boiling water and steep for 10 minutes.
Juice the lime and orange. In a blender purée the citrus juice, Serrano pepper, soaked guajillo chilies and 1/2 cup liquid from peppers, garlic, cumin, onion powder, salt and olive oil.
Pour over steak, turning to coat all over, and marinate 3 hours covered, in the refrigerator.
Notes
I use this marinade with either 2 lbs of skirt steak or flank steak.