In small saucepan stir together water, vinegar, sugar, mustard, salt, black pepper, and red pepper. Add lemon slice and onion. Bring to boiling; reduce heat. Simmer, uncovered, for 20 minutes. Stir in catsup, Worcestershire sauce, and liquid smoke. Return to boiling. Remove from heat; discard lemon slice. Makes about 1-1/2 cups.