Step 1

Preheat oven to 425°F. Toss cauliflower florets on a large rimmed baking sheet with onion, thyme, garlic, and oil; season with salt and pepper. Roast, tossing occasionally, until almost tender, 35-40 minutes—check after 30 minutes. Note: See notes above. I find 30 minutes to be consistently right for me, but every oven is different, so start checking at the 30 minute mark.

Step 2

Sprinkle with Parmesan, toss to combine, and roast until cauliflower is tender and golden, about 10 minutes.