Bring a large pot of water to a boil and cook the cauliflower until just fork tender, about 5 to 7 minutes. Drain well and let it cool.
In a large bowl, whisk together the mayonnaise, Dijon mustard, apple cider vinegar, paprika, salt, and pepper until smooth. Stir in the chopped hard boiled eggs.
Add the cooled cauliflower, celery, red onion, and fresh dill to the bowl.
Stir everything together until well coated.
Cover and refrigerate for at least 30 minutes before serving so the flavors have time to come together.
Do not overcook the cauliflower: Cook it just until fork tender so it still holds its shape and does not turn mushy once mixed with the dressing.
Drain it well: Let the cauliflower drain and cool fully before mixing so the salad does not get watery.
Mix the eggs into the dressing: Stirring the chopped hard boiled eggs into the dressing first helps distribute their flavor more evenly throughout the salad.
Chill before serving: Giving the salad at least 30 minutes in the fridge helps the flavors come together and improves the texture.
Adjust the texture to your liking: If you want it chunkier, cut the cauliflower into larger pieces. For a more classic potato salad feel, chop it a little smaller.