Combine steak, beer, 1 Tbsp. lime juice, 1 tsp. salt, and ¼ tsp. pepper in a resealable plastic bag. Seal; chill 3 hours.

Cook onion, garlic, and oil in a small skillet over medium heat until soft and translucent, 5 minutes. Let cool.

Prepare a grill for high heat (if using charcoal, prepare two zones of heat, high and medium-high). Grill tomatoes over high heat, turning occasionally, until well charred but still holding their shape, 6–8 minutes.

Reduce grill to medium-high heat (or use medium-high zone if using a charcoal grill). Remove steak from marinade and pat dry. Season with salt and pepper and grill until charred, about 3 minutes per side for medium-rare. Transfer to a cutting board and let steak rest 10 minutes.

Meanwhile, blend onion and garlic, tomatoes, chipotle, and remaining 3 Tbsp. lime juice in a blender until smooth. Add chopped cilantro, season with salt, and pulse until just combined. Transfer salsa to a small bowl.

Grill tortillas until soft and beginning to char, about 30 seconds per side. Slice steak against the grain into ½" strips. Top each tortilla with a few pieces of steak, then some salsa, cilantro leaves, avocado, and Cotija cheese. Serve with lime wedges for squeezing over.