1. Preheat oven to 425 degrees F. Spray an 8- or 9-inch square or round baking pan with cooking spray.
2. In a small bowl, whisk together olive oil, mustard, and lemon zest. Remove any green leaves from the cauliflower and trim the stem flush with the bottom of the head. Place cauliflower in prepared pan and brush mustard mixture over the entire head. Cover cauliflower with foil. Roast for 45 minutes, then remove foil and continue baking until fork tender and darkened, about 25 to 30 minutes longer. Let rest for 5 minutes, then transfer to a serving plate.
3. While cauliflower roasts, prepare the gremolata. Toast walnuts in a small skillet over medium heat, tossing occasionally, until fragrant and slightly darkened, about 5 minutes. Remove from pan, let cool, then finely chop. Place walnuts in a small bowl and mix with parsley, lemon juice, garlic, salt, and pepper.
4. To serve, bring roasted cauliflower to the table and cut into large wedges. Serve topped with gremolata.
Source: Hannaford fresh Magazine, September - October 2015