Pat the ribeye dry with paper towels. In a small bowl whisk together olive oil, lime juice, minced garlic, cumin, smoked paprika, kosher salt, and black pepper. Rub the marinade evenly over both sides of the steak. Cover and refrigerate 30–60 minutes (up to 2 hours). Remove from fridge 20 minutes before grilling to come to near room temperature.

Grill the steak

Preheat grill (or cast-iron skillet) to high heat (450–500°F / 230–260°C). Oil the grates lightly. Place the ribeye on the hot grill and cook until desired doneness: about 4–5 minutes per side for medium-rare (internal 125–130°F / 52–54°C), 6–7 minutes per side for medium. Use an instant-read thermometer for accuracy. Transfer steak to a cutting board and tent loosely with foil. Rest 8–10 minutes before slicing (this keeps juices in).

Slice

Slice the rested steak thinly across the grain into bite-size strips for tacos. Keep warm.

Grilled Onions

While steak rests, toss onion slices with oil and 1/2 tsp kosher salt. Grill on the hot grill or a cast-iron pan for 3–4 minutes per side or until nicely charred and softened. Remove and chop into 1/2" pieces if desired.

Green Salsa (Salsa Verde)

Roast tomatillos

Place husked tomatillos on a hot cast-iron skillet or under a broiler and roast 6–8 minutes, turning occasionally, until they are blistered and soft and lightly charred.

Blend

Add the roasted tomatillos, cilantro, jalapeño, chopped white onion, lime juice, salt, and 1–2 tbs water to a blender or food processor. Pulse until just combined but still slightly chunky. Taste and adjust salt or lime. If too thick, add additional water 1 tsp at a time to reach a spoonable sauce consistency.

Assembly & Garnish

Warm tortillas: Heat a dry skillet or griddle over medium-high heat. Warm tortillas 20–30 seconds per side until pliable and lightly charred. Keep wrapped in a clean towel to stay warm.

Assemble tacos: Place 2–3 tablespoons of sliced ribeye on each warmed tortilla. Top with grilled onions, a spoonful of green salsa, a sprinkle of crumbled cotija, and a few cilantro leaves. Squeeze lime wedge over tacos and add hot sauce if desired.

Serve: Arrange tacos on a platter and serve immediately while steak is warm.