In a small saucepan, cook and stir onion and butter over medium heat until onion is tender. Stir in ketchup, water, honey, lemon juice, Worcestershire sauce, and black pepper. Bring to boiling; reduce heat. Simmer, uncovered, for 5 minutes. Transfer sauce to a covered storage container. Cover and chill up to 24 hours. Pack in coolers with ice to tote.