Chop the onion and cut the pineapple very finely. Stir in the curry powder, salt, pepper and soy sauce. Add a little soy sauce (not too much, otherwise the sauce will be too thin). Then stir in the sour cream. Do not stir too hard, otherwise the sauce will be too runny.
I always make a sauce carousel in different colors for fondue / grilling: curry pineapple sauce (dark yellow), egg sauce (yellow), cucumber dill sauce (greenish), gypsy sauce (red), garlic sauce (white), cocktail sauce (orange / pink).