Pickled Red Onions:
Pickled Red Onions:
To prepare Pickled Red Onions, add peppercorns and thyme to 1-pint Mason jar; top with red onions. Combine tequila, honey and vinegar in small saucepan; bring to a boil over medium heat. Stir in salt until dissolved. Carefully pour hot tequila mixture over onions, making sure to cover onions completely. Close jar; let stand for 1 hour or until mixture reaches room temperature. Shake jar to dissolve salt. Refrigerate at least 24 hours before using.
To prepare Salsa, place yellow onion slices on grid over medium, ash-covered coals. Grill onion, covered, 12 to 14 minutes (over medium heat on preheated gas grill, covered, 12 to 14 minutes), turning occasionally. Roughly chop grilled onion; set aside to cool.
Combine grilled onion, cilantro, chipotle peppers, garlic, black pepper and 1/2 teaspoon salt in blender container. Cover; pulse on and off until pureed. With blender running, slowly add oil to blender through opening in cover, processing until smooth. Reserve 1 cup salsa; cover and refrigerate.
Place beef steaks and remaining salsa in food-safe plastic bag; turn steak to coat. Close bag securely and marinate in refrigerator 30 minutes.
Remove steaks from marinade; discard marinade. Pat steaks dry with paper towel; season with salt, if desired.
Grill, covered, 10 to 14 minutes (over medium heat on preheated gas grill, covered, 12 to 16 minutes) for medium rare (145°F) to medium (160°F) doneness, turning occasionally. Keep warm.
Place Cotija cheese and queso fresco in food processor container. Pulse on and off until cheese resembles coarse breadcrumbs. Cover and refrigerate until ready to use.
Carve steaks lengthwise into 1 inch strips, then across the grain into 1/2-inch pieces. Divide beef among tortillas; top with reserved 1 cup salsa, pickled onions, cheese, avocado, cilantro and lime wedges, as desired.
Nutrition information per serving: 672 Calories; 306 kcal Calories from fat; 34 g Total Fat; 7 g Saturated Fat; 20 g Monounsaturated Fat; 71 mg Cholesterol; 1225 mg Sodium; 51 g Total Carbohydrate; 5.1 g Dietary Fiber; 25 g Protein; 4.6 mg Iron; 4.2 mg Niacin; 0.5 mg Vitamin B6; 5 mcg Vitamin B12; 8.4 mg Zinc; 32.8 mcg Selenium; 95.3 mg Choline;