Tear up lettuce and put in the bottom of a large bowl. Break up cauliflower into bite size peices and add on top of lettuce, onion on cauliflower and bacon on onion. In a small bowl, mix mayo, sugar, vinegar, salt and pepper to taste. Stir until sugar is disolved. Spread on top of bacon then sprinkle parmesan cheese on top. DO NOT MIX until ready to serve.