In a small bowl, combine 2 tablespoons salt, 1 tablespoon black pepper, the brown sugar, coffee, garlic, chipotle powder, and red pepper flakes. Pat the steaks dry with paper towels, place them in a baking dish, and rub them all over with the olive oil. Rub the steaks on both sides with the spice mix, using it all. Cover the dish and refrigerate for at least 2 hours to allow the flavors to get into the meat.