FOR THE STEAK
2 teaspoons brown sugar
2 teaspoons chili powder
1 teaspoon salt
1 teaspoon cumin
1/4 teaspoon chipotle powder or a large pinch cayenne pepper
2 pounds skirt steak, trimmed of excess fat (or 2 pounds flank steak)
1. Prepare a two-tiered fire on your gas grill with a medium-high and a medium-low area, or on a charcoal grill with medium high and a low area.
2. In a small bowl, combine the sugar, chili powder, salt, cumin, and chipotle powder or cayenne pepper. Sprinkle the rub on all sides of the steak and set aside.
FOR THE SALSA
5 plum tomatoes, cored, halved, and seeded
2 red onions, sliced in 1/4-inch disks
2 jalapeno peppers
2 tablespoons olive oil
Salt and pepper, to taste
1 tablespoon balsamic vinegar
1/4 cup chopped cilantro
1. On a large, rimmed baking sheet, arrange the tomatoes, onions, and jalapenos. Brush with the oil and sprinkle with salt and pepper. Set the tomatoes (cut side up), red onions, and jalapenos on the hot part of the grill. Grill the vegetables, flipping every couple of minutes for 8 minutes or until they're lightly charred.
2. Set the jalapenos on a plate. Transfer the tomatoes and onions to the cooler side of the fire and continue to cook an additional 5 minutes so the tomatoes dry out a bit more and the onions soften.
3. Transfer all the vegetables to a cutting board and let cool for a couple of minutes. Core and seed the jalapenos. Chop the vegetables, toss with the vinegar and cilantro, and season generously with salt and pepper.
4. Meanwhile, grill the steak over the hot part of the fire, flipping after 3 minutes, for 6 minutes total, or until it registers 130 degrees on an instant-read thermometer for medium rare.
5. Let the steak rest for 5 minutes, then slice and serve with the salsa.