In a large saucepan, heat canola oil over medium heat.
Add onion and garlic and sauté until glassy, not brown about 3-5 minutes.
Add rhubarb and water. Cook 5 minutes or until rhubarb starts to soften.
Mix in brown sugar, tomato paste, cider vinegar, Dijon mustard, chili powder, cayenne pepper, and Worcestershire, salt, pepper and liquid smoke/smoked paprika. Bring to boil then simmer on low for 30 to 45 minutes until rhubarb breaks down and sauce thickens.
For a smooth finish, use an immersion blender or food processor to puree sauce.
Taste and adjust seasoning to your preference. Make it sweeter with sugar, tangier with vinegar or hotter with more cayenne.
Store in refrigerator for 7 to 10 days or in the freezer for up to 6 months.