Snip bacon strips into small pieces into a 2 quart casserole dish.  Microwave on high for 3 to 4 minutes, stirring after 2 minutes.  With slotted spoon, remove cooked bacon pieces to paper towels to drain.

Add sugar and cornstarch to bacon drippings in casserole dish, blending well.  Stir in salt, pepper and vinegar.  Morcrowave on high for 3 to 4 minutes, until thick.

Add drained beans and onion slices to sauce, stirring well.  Cover.  Microwave on high for 6 minutes, stirring after 3 minutes.  Let stand 10 minutes before serving to blend flavors.  Sprinkle cooked bacon pieces over top and serve.