Put the mayonnaise, vinegar, honey, olive oil, half the lemon juice, salt, and pepper into a medium bowl and whisk together.
Slice the avocado into 1/2" slices and spread evenly on a plate. Season with lemon, salt and pepper.
Mix the Brussels sprouts, apples, and cashews in a bowl and dress with the quick ranch. Add lemon juice, salt, and pepper to taste.
Evenly distribute the salad over the avocado. Serve immediately.