Place cauliflower on a parchment paper-lined cookie sheet, toss with 1-2 tbsp oil, and sprinkle with ~1/2 tsp sea salt. Roast at 425 degrees on the middle rack for about 30 minutes, checking/stirring every 1- minutes.
While the cauliflower is cooking, prepare the onion. Heat about 1 tbsp of oil in a medium-sized frying pan over medium-high heat. Add the onions. Continue cooking and stirring until onions start to brown (about 5 minutes). Add vinegar, maple syrup, 1/2 tsp salt, garlic powder and continue cooking until the liquid evaporates- another 5 minutes or so. Adjust the heat down slightly if needed.
Remove the cauliflower from the oven and allow it to cool for about 10 minutes before assembling the salad.
Assemble the salad starting with the arugula, then top with cauliflower, onions, and avocados. Drizzle with oil and balsamic vinegar. Serve!
Notes
I find it’s best to let the cauliflower get a head start in the oven for a few minutes before you start cooking the onion because it takes such a short time to cook. That way both finish around the same time and you can serve them warm. If you cook the onions a little early and find that they get cold while the cauliflower is still cooking, simply warm them in the microwave for about 20 seconds and they’ll be good to go.