Combine the water, malt vinegar, orange juice, tomato paste, dark brown sugar, molasses, raisins, Worcestershire sauce, Dijon mustard, garlic powder, onion powder, black pepper, cayenne pepper, and kosher salt in a medium saucepan and whisk until smooth.
Bring to a gentle simmer over medium heat, then reduce to medium-low and cook, stirring occasionally, 20–25 minutes until the raisins are very soft and the sauce has thickened slightly.
Carefully blend until completely smooth using an immersion blender, or transfer to a blender and purée until velvety, 1–2 minutes; return to the saucepan if needed.
Simmer the blended sauce over low heat, stirring, 5–10 minutes until it coats the back of a spoon and a finger swiped across the spoon leaves a clear line.
Let cool to room temperature, then transfer to a clean bottle or jar. Refrigerate at least 12 hours before serving for flavors to meld. Keep refrigerated and use within 1 month.