To marinate the meat: Combine olive oil, chipotle chiles, garlic, zest and juice from both the orange and lime, 3/4 teaspoon salt and the pepper in a blender. Blend until smooth. Pour marinade into a large resealable bag or bowl. Add steak and toss to coat. Marinate at least 30 minutes at room temperature or chill up to overnight in refrigerator, turning the bag occasionally.
To prepare the pickled red onions: Combine vinegar, 1/2 cup water, honey and 1/2 teaspoon salt in a small saucepan. Bring to a simmer over medium heat. Add onions and remove from heat. Let onions sit in the vinegar mixture for 10 minutes. Drain and reserve onions.
To cook the meat: Remove steak from marinade, shaking off any excess. Heat vegetable oil in a large cast-iron skillet over medium-high heat. Arrange meat in the skillet and cook, turning frequently, for 3 to 4 minutes a side, until an instant-read thermometer inserted into the center reads 115 to 120 degrees for medium-rare or 125 to 130 degrees for medium. Let rest 10 minutes before thinly slicing against the grain.
To assemble the tacos: Warm tortillas in a microwave, oven or over a gas flame. Divide steak among tortillas, then top with, avocado, cheese, cilantro and pickled onion. Serve with lime wedges on the side.
Nutrition information per taco with 1 tablespoon Cotija:
Calories230Fat13 gSodium245 mg