In a medium saucepan, mix together the ketchup, apple cider vinegar, water, brown sugar, tamari (or soy sauce), yellow mustard, garlic powder, ground cumin, onion powder, and smoked paprika until well blended.
Place the saucepan over medium heat and bring the mixture to a gentle simmer, stirring occasionally to prevent sticking and to dissolve the sugar.
Reduce the heat to low and let the sauce simmer gently for about 20 minutes, stirring often to ensure it doesn’t burn and to allow the flavors to meld and the sauce to thicken.
Taste the BBQ sauce and adjust seasoning if needed. Once thickened and flavorful, remove from heat, allow to cool, then transfer to a container and store in the refrigerator for up to 2 weeks.
