Preheat your oven to 425°F (220°C) and line a baking sheet with aluminum foil, spritzing it with non-stick cooking spray.

Coarsely chop rhubarb and peel garlic, then spread them on the baking sheet and roast for 15 to 20 minutes until tender and aromatic.

Transfer the roasted mixture to a food processor and add 1 cup of water; puree until smooth to create the sauce base.

In a saucepan, combine the puree with balsamic vinegar, brown sugar, ketchup, Worcestershire sauce, chili powder, cinnamon, cayenne pepper, salt, and black pepper, then stir well.

Simmer the mixture over medium-low heat for 10 to 15 minutes, stirring occasionally until it reaches desired thickness.

Allow the sauce to cool to room temperature, then transfer to airtight containers for storage.