Trim the cauliflower of leaves and stem, leaving enough core to keep the head whole.
Have ready a large pan with an inch of boiling water. Steam the cauliflower in it, covered, for 10 minutes.
Line a baking sheet with baking paper, or grease it well with butter. Preheat the oven to 400° F (205° C).
In a large bowl, blend yogurt with all remaining ingredients except cheese.
Remove cauliflower carefully from pan. Turn it, head-down, into the bowl. Move it around gently to cover as much of the surface as possible with the yogurt blend. Spoon more yogurt into the spaces between the florets. Turn right-side-up and massage more yogurt all over it.
Press the grated cheese all over the surface, as much as possible. Place it on the baking sheet.
Roast the cauliflower 40-50 minutes, until well crusted and tender. Check for done-ness by inserting a thin knife into the thickest part, on the bottom.