Prepare the cauliflower by cutting the head into bite-sized florets and steaming until the cauliflower is only slightly tender, about five to seven minutes.
Set aside to cool.
Peel the eggs and reserve two yolks; dice the remainder and set aside.
Make the dressing by whisking together sour cream, mayonnaise, vinegar, mustard, celery seed and salt.
Mash the two reserved yolks in the cream mixture and whisk until very smooth.
Add the cooled cauliflower, diced eggs, celery, onion and dill.
Stir to coat.
Refrigerate for about one hour to completely cool the cauliflower and allow the flavors to meld together.
Garnish with green onions and serve cold