• Kosher salt and freshly ground pepper
• 1 1/2 to 1 3/4 lb. flatiron or flank steak
• Vegetable oil, for the grill
Grate the zest of 1 lime; cut the lime in half. Combine zest with the chili powder, brown sugar, thyme, cumin, chipotle powder, 1/2 teaspoon salt and a few grinds of pepper in a small bowl. Squeeze the zested lime over the steak and use the lime halves to rub the juice into the meat. Rub the spice mixture on both sides of the steak. Let stand at room temperature, 30 minutes.
Meanwhile, preheat a grill to medium-high. Brush the grates with vegetable oil. Grill the steak until it's well browned with nice grill marks, about 8 minutes. Flip and grill until a thermometer inserted sideways into the center registers 125 degrees, about 5 to 7 more minutes for medium-rare (the thinner edges of the steak will be cooked to medium).