In a small saucepan, over medium heat, melt butter, add onion, and sauté for about 1 minute, add garlic, and sauté for about 30 seconds, long enough for the garlic flavour to release. Then add rhubarb, and water, then cook at lower temperature for about 10 minutes, long enough for the rhubarb to soften.
Then add maple syrup, ketchup, apple cider vinegar, Worcestershire sauce, Dijon, ginger, chili powder and salt.
Simmer uncovered, stirring occasionally, until the flavours are well blended about 10-15 minutes and once the sauce becomes syrupy, remove from heat and set aside.
Store in the refrigerator in an air-tight container for 7-10 days.
