Step 1) Combine steak, oil, lime juice, steak seasoning, ancho chile and vinegar in a large resealable plastic bag turning to thoroughly coat the meat.
Step 2) Marinate at room temperature for at least 15 minutes or make ahead and refrigerate overnight.
Step 3) Preheat grill to medium-high heat. Spray grill with grill spray. Remove steak from marinade; discard marinade. Grill the steak over Direct Medium heat for 3 to 5 minutes per side or to desired doneness. Transfer cooked meat to a cutting board and allow meat to rest for 5 minutes. Slice the steak across the grain into very thin slices.
Step 4) To assemble the quesadillas, arrange cooked steak slices in a single layer over one half of each tortilla. Sprinkle with cheese. Fold each tortilla in half over the filling pressing firmly. (The quesadillas can be made up to this point, covered and refrigerated for up to 6 hours ahead of time.)
Step 5) To grill the quesadillas, heat grill or grill pan to medium heat. Spray grill with grill spray, place prepared quesadillas on grill and cook over Direct Medium heat for 2 to 3 minutes per side or until grill marks appear and cheese is melted. Transfer cooked quesadillas to a cutting board and cut into wedges. Serve immediately with salsa.
Step 6) To make the Avocado Tomato Salsa, combine all ingredients in a bowl, stir and season to taste with salt and pepper.
Recipe Tip: For added spicy heat and a deep smokey flavor, stir cooked steak slices with 1 to 2 teaspoons of canned chipotle in adobo sauce prior to placing on tortillas.