Wash cauliflower.
Remove outer leaves from cauliflower head.
Cut cauliflower int four parts for faster cooking.
Boil about 3 quarts of water in a large pot
Add cauliflower to water and heat to boiling.
Add 1 teaspoon of salt and juice of half a lemon to water
Boil for 10-12 minutes until cauliflower is tender.
While cauliflower is cooking, mix together the cheese, mayonnaise, onion, 1/2 teaspoon of salt, mustard and parsley in a small bowl.
Microwave cheese sauce 2-3 minutes.
Drain cauliflower and cut into bite-sized pieces.
Mix cooked cauliflower with cheese sauce and serve.