Wash the cauliflower heads, remove the outer leaves, and trim the very bottom of the core, keeping the core intact. Slice each cauliflower head into ¾-inch-thick slices. The outer slices will fall apart - simply roast them as florets with the steaks. Plan on getting three steaks out of each cauliflower head.

Arrange the steaks in a single layer on the baking sheet. Scatter the florets around them. Spray their tops with olive oil and sprinkle them with half the seasonings.

Bake the cauliflower slices for 15 minutes. Remove them from the oven, carefully flip them using two wide spatulas, spray them with more oil, and sprinkle them with the remaining spices.

Return the cauliflower steaks to the oven and bake them until browned and fork-tender, 10-15 more minutes. Serve immediately.