Preheat the oven to 220C and line a baking tray. Rub the cumin and olive oil over the cauliflower slices, then season with salt and pepper. Place on the baking tray and roast for 15-20 minutes, or until tender and crisp on top.
In the meantime, mix together the ingredients for the chimichurri, then season to taste. Serve the cauliflower steaks with spoons of chimichurri.