Be sure to use the freshest baguette possible for this easy steak sandwich.
Peel, and cut onions into 1/2-inch-thick rings. Heat 2 tablespoons of oil in a large skillet over medium-high heat; add onions, cook until brown and tender, 10 to 15 minutes. Season with salt and pepper; remove onions to a plate.
Heat another tablespoon oil in same skillet over high heat. Season steaks with salt and pepper; cook 30 seconds on each side; remove steaks to plate. Add Worcestershire sauce and 2 tablespoons water to skillet, scraping up browned bits; return onions to skillet and toss to coat.
Cut up steaks; sandwich steak and onions between bread.