Preheat a grill or grill pan to medium-high heat.
In a medium bowl, combine the steak, chili powder and 1 tbsp. of the EVOO. In another medium bowl, toss together the tomatillos, avocado and lime juice; season with salt and pepper.
Thread steak, poblano and onion onto 4 skewers. Brush with remaining 2 tbsp. EVOO and season with salt and pepper. Grill, turning frequently, until the steak is cooked and the onion and pepper are browned in spots, 6 to 8 minutes.
Grill tortillas, turning frequently, until soft, 1 to 2 minutes. Serve skewers with tortillas, tomatillo relish and lime wedges.