Remove the stems from all the dried chilis, then shake out and discard the seeds. Place the chilis in a small saucepan with water just to cover. Bring to a boil, remove from the heat and let stand for 20 minutes to soften. Drain.
In a small, dry frying pan over medium heat, toast the cumin seeds until lightly browned and fragrant, 2 to 3 minutes. In a blender, combine the softened chilis, cumin seeds, garlic, jalapeno chili and red wine vinegar. Puree until thick and smooth, 1 to 2 minutes. Add the olive oil and salt and blend again until well mixed.
Place the skirt steak in a shallow non-aluminum dish and pour the marinade over it. Let marinade at room temperature for 1 hour.
Prepare a fire in a charcoal grill or preheat a broiler.
To prepare the Relish:.
In a small bowl, stir together the onion, Serrano chili, cilantro, salt, lime juice and olive oil. Set aside until you are ready to serve.
When the fir is hot or the broiler is ready, place the steak on the grill rack about 3 inches from the coals, or place in a broiler pan at the same distance from the heat source. Grill or broil, turning once, until seared on the outside but still pink in the center, 1 to 2 minutes per side.
Slice the steak across the grain and on the diagonal. Arrange the slices on a platter and serve with the relish on the side.