Preheat oven to 400 degrees F.
Cut off bottom stem of cauliflower so it will sit flat and slice vertically into four thick slabs. Place cauliflower on foil or parchment lined baking sheet. Drizzle with oil, salt, and pepper. Bake for ~30 minutes, turning over once, until tender and golden brown.
In bowl, mix together zest, juice, olives, mustard, vinegar, and coriander.
Serve cauliflower with sauce.