Skirt Steak Quesadillas

Name: Skirt Steak Quesadillas
Ingredients: 2 tablespoons chili powder; 2 teaspoons kosher salt; 1 teaspoon ground cumin; 1/2 teaspoon chipotle powder; 1/2 teaspoon cayenne pepper; 1 teaspoon lime zest; 1 1/2 pounds skirt steak; Twelve 6-inch corn tortillas; Vegetable oil, for brushing; 1 1/2 cups shredded peppered Monterey Jack cheese; Tomatillo Guacamole, recipe follows; Fresh cilantro, for serving; Lime wedges, for serving; Sour cream, for serving; 3/4 cup coarsely chopped fresh cilantro leaves; 1 teaspoon salt; 6 to 8 tomatillos, husked and coarsely chopped; 2 cloves garlic, smashed and quartered; 1 avocado, halved, pitted, and diced; 1/2 jalapeno, coarsely chopped with seeds; Juice of 1 lime; 1/2 onion, coarsely chopped