1. Preheat oven to 400 degrees F. Place sweet potatoes and red onion slices in a medium bowl. Drizzle with olive oil and season with salt and pepper. Toss together and then put them on a large baking sheet. Bake in the oven for 30 minutes, or until sweet potatoes are tender. Stir a few times while baking.
2. Drizzle kale with 2 tablespoons of balsamic vinegar. Season with salt and pepper and place on a baking sheet. When the sweet potatoes and onions have been in the oven for 15 minutes, put the kale in the oven. Bake for 15 minutes, or until kale is wilted and starting to get a little crispy.
3. While the vegetables are roasting, make the quinoa. Using a strainer, rinse the black quinoa under cold water. Add quinoa, water, and salt to a medium saucepan and bring to a boil over medium heat. Boil for 5 minutes. Turn the heat to low and simmer for about 15 minutes, or until water is absorbed. Remove from heat and fluff with a fork. Let cool quinoa cool to room temperature.
4. When the vegetables are done roasting, let them cool to room temperature. Chop up the red onion slices and kale. In a large bowl, combine quinoa, sweet potatoes, red onion, and kale. Drizzle the salad with remaining three tablespoons of balsamic vinegar and add in the dried cranberries. Stir to combine. Season with salt and pepper and serve.