Shred broccoli, cabbage & jicama in food processor using the grater disc. In a large bowl, combine the shredded broccoli, cabbage, jicama and the chopped red onion.Whisk together the mayonnaise, lemon juice, vinegar, salt, and a generous quantity of fresh pepper. Pour the dressing over the broccoli mixture and stir to combine. Taste and add more salt or pepper, if needed.Allow to sit for at least 30 minutes (or an hour in the fridge) so the flavors can mingle. Up to 24 hours would be ok.Serve with sliced avocado and macadamia nut gremolata.