Season the steak liberally with salt and pepper, and allow to sit at room temperature for 15 to 30 minutes. Meanwhile, heat a grill pan over medium-high heat. Brush the steak with vegetable oil and cook on grill pan, undisturbed for 3 minutes. Flip the steak over and cook until the steak is 130 degrees F for medium rare, about 3 minutes more. Remove to a cutting board, and allow to rest a full 5 minutes before slicing. Cut the steak with a sharp knife against the grain into thin slices. Fan slices out onto a serving platter and top with the Poblano Pesto.
Char the poblano peppers on top of a gas burner, on a grill, or under the broiler) until all of the sides are blackened. Place in a bowl covered tightly with plastic wrap, allowing the steam to help loosen the skin. With your fingers or a spoon, scrape and discard the blackened skin then remove the seeds and core. Coarsely chop the poblanos, and place into a mini food processor. Add the Parmesan, cilantro, garlic, chili powder and oil and process until well combined, but not totally smooth. Taste and season with salt.