Mix the marinade ingredients in a small bowl and rub the marinade onto cauliflower head evenly until well coated. Place cauliflower on a baking tray and bake for 50 minutes.
Mix mustard, pesto, olive oil and lemon juice in a small bowl. Remove cauliflower from the oven and brush cauliflower with mustard and pesto sauce evenly. Serve whole cauliflower with the remaining sauce in a separate serving sauce plate.