Preheat oven to 425°F (220°C).
Chop your cauliflower into small florets (no larger than 1 inch on any side), and place it into your mixing bowl.
Dice the onion and mince the garlic, and slide them on top of the cauliflower.
Measure out all the spices in a bowl, then the olive oil and lemon juice. Mix them all together in a separate small bowl, or simply pour them all on top of the cauliflower, onion, and garlic mixture.
Toss everything together in the bowl until each floret has been coated with a thin layer of oil, then arrange them in a single layer on the silicone mat (placed on top of your baking sheet).
Bake the mixture for 20 minutes, then take the tray out of the oven and use a spatula to move around the mixture. Rotate the tray to the other side, then bake for another 15 minutes.
DING! If it's done enough for you after 35 minutes, take it out now, but since I usually work with frozen cauliflower, at this point I move around the mixture one more time and bake for another 10 minutes to let it all crisp up even more. I like to eat most of mine off the pan initially, then tupperware the rest for the freezer, but I live alone so you do what you need to.