A very simple recipe from my mom, tastes great with fondue or prawn cocktail. Can be modified with dill and a splash of lemon juice.
Mix the ketchup and mayonnaise (if you like it less calories use salad cream) and add cognac to taste.
You can vary the amount of ketchup you add, it`s a matter of taste. So the first time it is better to add the ketchup gradually until the desired taste intensity is achieved.