Lay the steak out on a large platter or piece of plastic wrap and rub both sides with the Ancho Chili Powder. Marinate for 1 hour so the flavors can penetrate the meat.
In the meantime, place a large grill pan on 2 burners over medium-high heat or preheat an outdoor gas or charcoal barbecue and get it very hot. Brush the grates with oil to keep food from sticking. Rub the peaches with oil and season with salt and pepper. Put the peaches cut-side down on the grill and cook for 5 to 8 minutes, until the flesh softens slightly and caramelizes. Turn them over with tongs and grill the other side for 3 minutes to char the skin; remove to a platter. Grill the lime slices for 2 minutes each side until slightly charred.
Scrape off the excess chili powder on the surface of the steak so it doesn't burn on the grill. Rub the steak with oil and season both sides with of salt and pepper. Grill the steak on the hottest part of the barbecue for 4 minutes per side, until well charred. Transfer the steak to a cutting board and let stand for 5 minutes. Cut the meat across the grain on the diagonal.
To serve: put the greens on a platter and arrange the peach halves, lime slices, and steak on top. Sprinkle with the pecans and drizzle the salad with the olive oil.
This homemade chili powder will add a smoky depth to chili and as a dry rub for steaks. Toast the ancho chile pieces over low heat in a dry skillet until fragrant, shaking the pan so they don't scorch. Put the chiles in a mini food processor and pulse to a powder. Add the remaining ingredients and buzz again to combine.
Yield: about 1 cup