Preparation

• Prepare a medium (375°F) gas or charcoal grill fire.
• Meanwhile, in a small bowl, mix the ancho powder with 1 tsp. of the sugar, 2 tsp. salt, and 3/4 tsp. pepper. Pat the steak dry, sprinkle the ancho mixture on both sides, and let sit at room temperature while the grill heats.
• Set the onion rounds and jalapeños on a large plate and sprinkle with 1 Tbs. of the oil, 1/2 tsp. salt, and 1/2 tsp. pepper.
• In a large bowl, toss the cabbage with the lime juice, the remaining 1 tsp. sugar, and 1/2 tsp. salt. Add the remaining 1 Tbs. oil and toss again.
• Put the steak, onions, and jalapeños on the grill. Grill the steak, flipping once, until cooked to your liking, 5 to 6 minutes for medium rare (130°F to 135°F). Grill the vegetables, flipping once, until grill marks appear and they’re just tender, 4 to 6 minutes for the jalapeños and about 8 minutes for the onion. (Move the onions to a cooler part of the grill or lower the heat if they start to burn.) Transfer the steak and vegetables to a cutting board; let the steak rest for 5 minutes.
• Chop the onions and finely chop the jalapeños, add to the cabbage mixture, and toss well. Season to taste with salt, pepper, and lime juice.
• Spread 4 tortillas on the grill and heat, flipping once, until warm and softened, about 1 minute. Stack the warmed tortillas in a kitchen towel; repeat with the remaining tortillas.
• Thinly slice the steak and put a few slices on each of the warm tortillas. Top with the slaw and a dollop of sour cream. Serve with the lime wedges.