Heat a broiler with a rack about 4 inches from the heat and line a rimmed baking sheet with aluminum foil.
Combine the avocado, radishes, cilantro, jalapeno pepper, lime juice and oil in a small bowl. Place plastic wrap touching the surface over it to prevent the avocado from browning.
Place steak on aluminum foil lined baking sheet. Rub both sides with ground cumin and salt and pepper. Broil about 3-4 minutes per side for medium rare. Transfer to a cutting board, tent with aluminum foil and allow to rest for 5 minutes.
While the steak is broiling, wrap tortillas in a damp paper towel and microwave for about 1 to 2 minutes, or wrap in foil and warm in the lower third of the oven for about 5 minutes.
Cut steak crosswise into 2 inch-wide pieces, thinly sliced on the diagonal. Place steak on the tortillas and top with salsa. Serve with a lime wedge.