Fry the bacon and set onto a paper towel to drain any extra grease. Let cool completely.
Finely chop the onion.
Cut the lettuce into small pieces. Cut the cauliflower into small florets.
In a small bowl, prepare the dressing. Whisk together the mayo, vinegar and sugar.
Combine lettuce, cauliflower, bacon, cheese, and onion into a bowl. Add the dressing and mix.