Prep your mix-ins: Finely chop the dill relish and onion so the dressing is smooth and spoonable. Smaller pieces mean better flavor distribution.
Combine the base: In a medium bowl, whisk together the mayonnaise and sugar-free ketchup until fully blended and creamy.
Add flavor: Stir in the relish, onion, pickle juice, sweetener (if using), Dijon mustard, paprika, garlic powder, salt, and pepper.
Adjust texture: If you prefer a thinner dressing, whisk in heavy cream or almond milk a little at a time until you reach your desired consistency.
Taste and tweak: Add more pickle juice for tang, more sweetener for balance, or extra paprika for warmth.
Season with salt and pepper as needed.
Chill: Cover and refrigerate for at least 30 minutes. Resting deepens the flavors and helps everything meld.
Serve: Spoon it over salads, use it as a burger sauce, or serve as a dip with veggies or grilled shrimp.