In a large cast-iron or other heavy skillet, cook beef and onion over medium heat until beef is no longer pink and onion is tender, 6-8 minutes; crumble beef. Drain and return to pan., Drain tomatoes, reserving 1/2 cup liquid. Stir tomatoes, reserved liquid, corn, chiles and salt into beef mixture; bring to a simmer. With the back of a spoon, make 6 wells in beef mixture; add an egg to each well. Sprinkle with pepper. Cook, covered, until egg whites are completely set, 5-7 minutes., Sprinkle with cheese. Serve with tortillas and toppings as desired.