Cut the broccoli up in florets and and blanch for 5 minutes by pouring boiling water over it. After 5 minutes strain the broccoli and refresh by running cold water over the broccoli while still in the strainer.
Fry onions in oil over moderate heat till glassy but not brown. Add to broccoli.
Fry chopped bacon in same pan. Add to broccoli.
Mix the sugar, lemon juice, vinegar, and mayonnaise together and pour over the salad. Toss together well. Allow to marinate in fridge for at least 2 hours. Can keep up to 4 days.