Preheat the oven to 500° F.
Remove the cauliflower leaves and cut the stem so that the base is flat.
Cut off two sides of the cauliflower so it will have a boxy shape. (You can save the sides for salad, or roast them along with the steaks.) Set the cauliflower on its base and slice it in half. Then slice each half in half. Some florets may fall away; save or roast them.
Place the steaks on a parchment-lined baking sheet. Spray lightly with cooking spray. This helps them become golden and slightly crisp. Sprinkle with the seasoning.
Cover the baking sheet with foil and put into the hot oven for five minutes.
After five minutes, remove the foil and return the steaks to the oven. Roast for another 10 minutes. They should be tender by this time.
To make the mousse, add the avocado, yogurt, and lime juice to a food processor and process until creamy.
Options for accompaniments are hummus, red pepper-walnut spread, or chimichurri. I serve it with rice, and like to sprinkle toasted chopped walnuts or pistachios on top, for crunch.
