Place the mayonnaise in a bowl. Add the tablespoon of ketchup. This gives the sauce its gentle pink color and a small touch of sweetness without overpowering the flavor.
Melt the butter and let it cool slightly before mixing. Sprinkle in the paprika, garlic powder, sugar, and vinegar.
Add water one tablespoon at a time. Yum yum sauce should be thin enough to drizzle but not watery. Usually 2–4 tablespoons is enough. Stir until smooth
Cover the bowl and refrigerate for at least 1 hour. The sauce changes dramatically as it chills — it becomes smoother, softer, and much more flavorful.
