In a bowl stir together 1/2 teaspoon of the kosher salt or 1/4 teaspoon salt, cumin, chili powder, oregano, and brown sugar. Rub into both sides of steaks. Lightly coat a grill pan with nonstick cooking spray. Preheat pan over medium-high heat. Add steaks. Reduce heat to medium. Cook for 8 to 10 minutes or until desired doneness, turning occasionally. (Or for a charcoal grill, place meat on rack of uncovered grill directly over medium coals. Grill for 9 to 11 minutes or until desired doneness; turn once. For gas grill, preheat grill. Reduce heat to medium. Place meat on grill rack over heat. Cover; grill as above.)
For salsa, in large skillet cook and stir onion and garlic in hot oil over medium heat until tender. Stir in tomatoes, chipotle, lime juice, and 1/4 teaspoon salt. Cook and stir 1 minute. Transfer to a bowl; stir in cilantro. Cut each steak in half; serve with salsa. Makes 4 servings.