Crumble hamburger into 2 quart casserole; add onion.
Microwave uncovered until meat is firm, 5 to 6 minutes.
Stir to break up meat; drain.
Stir in pork and beans, barbecue sauce and salt.
Cover and microwave to boiling, 3 to 4 minutes.
Prepare Com Bread Topping.
Spoon onto meat mixture, forming a ring of com bread around side of dish.
(Topping will cook toward center.) Microwave uncovered 2 minutes; turn dish one quarter turn.
Microwave until topping is no longer doughy, 2 to 3 minutes.