Cut a thin slice off the top of each tomato and discard; remove core. Carefully scoop out pulp, leaving a 1/2-in. shell. Reserve 1/2 cup pulp (discard remaining pulp or save for another use). Invert tomatoes onto paper towels to drain.
In a nonstick skillet, cook beef and onion over medium heat until meat is no longer pink; drain. Stir in the basil, salt, golden mushroom soup, sourcream,red pepper and reserved tomato pulp; bring to a boil. Reduce heat; simmer, uncovered, for 10-12 minutes or until the liquid has evaporated.
Stir in the rice, cheese and egg; heat through. Spoon into tomato shells. Place in a shallow 2-qt. baking dish coated with nonstick cooking spray. Bake, uncovered, at 350 degrees F for 20-25 minutes or until heated through.