Roast Beef should be thinly sliced and there should be 8 to 10 slices.
Mix catsup, brown sugar, lemon juice, worcestershire sauce, mustard, onion
salt, and pepper in 2-cup glass measure.
Microwave uncovered on high 1 1/2 minutes; stir. Microwave to boiling, 1 to 2 minutes.
Layer half the beef slices and half the sauce in 1-Qt casserole; repeat.
Cover and microwave on high until hot (1 1/2 to 2 1/2 minutes.)
Place bottom halves of buns on serving plate.
Top with beef and reamining bun halves.
Microwave uncovered on high until buns are hot.
Serve with french fries or chips!