Make the Chipotle Spice Rub and Brown Butter Breadcrumbs, and set aside.
Preheat the oven to 400° F. Slice the cauliflower head in half through the central stalk. Slice each half into two halves. You should have 2 thick cauliflower slabs that are intact. Some florets will crumble off the slabs towards the ends. Reserve the florets for this recipe. Wrap the remaining cauliflower for another use, and store in the refrigerator.
Rub both the slabs and florets with olive oil and the Chipotle Spice Rub.
Heat some olive oil in a sautè pan over medium-high heat, and sear the cauliflower slabs until slightly crisped - about 3 minutes per side.
Place on a baking sheet along with the florets, and roast until tender, about 15 minutes.
Spoon the citrus salad (below) onto a serving plate, and arrange the cauliflower steaks over the salad. Add a dollop of pesto and a sprinkling of breadcrumbs.