1. Heat a grill to medium-high (350° to 450°). In a small bowl, combine coffee, chile powder, 2 tsp. salt, and the brown sugar. Rub all over steak and let sit. Rub green chiles, apple, and onion with oil and season to taste with salt and pepper.
2. Grill steak, turning once (dry rub on meat will be very dark), 8 to 10 minutes total for medium-rare. Meanwhile, grill chiles, apple, and onion until lightly charred all over, 6 to 8 minutes.
3. Transfer everything to a cutting board, tent steak with foil, and let rest 5 minutes. Meanwhile, chop chiles, apple, and onion and transfer to a medium bowl. Stir in oregano and lime juice and season to taste with salt and pepper.
4. Thinly slice steak against the grain and top with chile-apple relish.
*Find ancho chile powder at well-stocked grocery stores.