Wrap Cauliflower head in plastic wrap and microwave for nine minutes or until tender.
Mix 1/2 cup mayo, 1 tsp minced onions, 1 tsp perpared mustard, 1/4 tsp salt and pour over top of cauliflower. Grade about 1/2 cup of cheese and put on top. Put in microwave long enough to melt the cheese.
Easy and delicious!