Preheat oven to 425 degrees. Toss together potato, onion, and 2 tablespoons oil on a rimmed baking sheet. Season with salt and pepper. Bake, stirring once, until potato and onion are tender, 24 to 26 minutes
Heat a large saute pan over medium heat. Add 2 tablespoons of olive oil, onion, garlic, crushed red pepper flakes, salt, and pepper and cook for about 5 minutes. Add the kale and 2 tablespoons of Dijon mustard. Cover and let steam and cook for 5 minutes, until the kale is soft.
Combine steamed kale lemon juice, white vinegar and parmesan cheese in a food processor or blender. Pulse until well combined. While it’s still blending slowly pour in olive oil in a slow steady stream. When consistency is to your liking season with salt and pepper to taste. This will be more pesto than you need. Transfer about half of the pesto, which should be about 1 to 2 cups total sealable container and pop in the freezer. It will be great to have on hand for a super easy meal down the road.
Cook pasta according to package directions, reserving ½ cup pasta water before draining. Toss pasta with roasted vegetables, pesto, and pasta water. Serve hot with extra cheese grated on top.