Homemade Sloppy Joes

1/2 c. onions, chopped
1/4 c. celery, chopped
1 Tbsp. butter
2/3 c. ketchup
1/2 c. water
2 lbs. lean ground beef
2 Tbsp. lemon juice
1 Tbsp. brown sugar
1 1/2 tsp. Worcestershire sauce
1 1/2 tsp. salt
1 tsp. vinegar
1/4 tsp. dry mustard

*Saute onion & celery in butter. Add 2 lbs. ground beef. Brown lightly. Drain off excess fat. Add rest of ingredients. Simmer, covered for 30 min.