In a medium saucepan, heat vegetable oil over medium heat. Add the finely chopped onion and bell pepper. Saute until softened, about 5 minutes.

Stir in kosher salt, chilli powder, dry mustard, cumin, smoked paprika, granulated garlic, and red pepper flakes (if using). Cook for 1–2 minutes until fragrant.

Mix in the molasses, honey, apple cider vinegar, and brown sugar. Stir well to dissolve the sugar.

Add crushed tomatoes, chopped sweet peppers, ketchup, Worcestershire sauce, and huckleberries (or blueberries). Bring the mixture to a simmer.

Reduce heat to low and let the sauce simmer uncovered for 30–40 minutes, stirring occasionally, until thickened.

For a smoother consistency, carefully blend the sauce using an immersion blender or in batches using a regular blender.

Stir in butter (if using) for extra richness. Let cool, then transfer to a sterilized jar or airtight container. Store in the refrigerator for up to 2 weeks or freeze for longer storage.