Preheat a grill or indoor grill pan to high.
Heat 1 tablespoon olive oil in a large skillet over high heat. Add the onion and bacon and cook until the bacon is crispy. Remove the onion and bacon from the pan. Add the balsamic vinegar and 1 tablespoon olive oil to the skillet and reduce for 2 to 3 minutes. Remove from the heat and set aside. Brush the romaine with the remaining 2 tablespoons olive oil. Place on the grill cut-side down and quickly sear until grill marks are visible. Set aside. For each serving, place a half head of romaine cut-side up on a plate and drizzle the balsamic dressing on top. Sprinkle with blue cheese and the bacon and onion, and garnish with cracked black pepper. Photograph by Yunhee Kim
Recipe courtesy Guy Fieri for Food Network Magazine