In a large bowl, combine cauliflower, red onion, ¼ cup olive oil, and Kosher salt. Toss to coat. Transfer vegetables to a baking sheet, single layer, and roast for 20-25 minutes, until cauliflower starts to brown. Once vegetables are done, transfer to bowl and stir with scallions.
Whisk together 2 tablespoons olive oil, lemon juice, and Dijon mustard. Pour over vegetables and toss to coat. Arrange vegetables on a platter. Top with pomegranate arils, pine nuts, and cilantro. Serve warm.