Preheat oven to 450°F. Place cauliflower and onion in a baking pan. Drizzle with olive oil and sprinkle with 1/2 tsp. of the salt. Stir to coat. Spread in an even layer. Roast, uncovered, 30 minutes or until tender, stirring in cranberries halfway through. 2. Meanwhile, in a small saucepan whisk together balsamic vinegar, honey, the remaining salt, and pepper. Simmer, uncovered, until slightly thickened, about 10 minutes. Pour over cauliflower mixture; stir to coat. Transfer to a serving dish. Sprinkle with mint.