Roast the vegetables. Heat the oven to 425°F. Place the squash and red onions in a single layer on a rimmed baking sheet. Drizzle with 2 Tablespoons of the oil and use your hands or a large spoon to toss to coat. Season with a pinch of salt and pepper and spread into an even layer. Roast until the squash is fork tender and vegetables are starting to brown, about 30-35 minutes, stirring halfway through. Remove the roasted vegetables from the oven and set aside.
Cook the quinoa. To cook quinoa on the stovetop: Add two cups of cold water to a medium pot. Add the rinsed and drained quinoa. Bring the mixture to a boil, then cover with a lid and reduce the heat to low. Simmer for 15 minutes, then take the pot off the heat. Let it sit, with the lid on, for 10 minutes. Remove the lid and fluff with a fork.
Toast walnuts: Heat a large frying pan over medium-high heat. Add the walnuts to the hot, dry pan, heated over medium high heat. Cook, keeping an eye on the walnuts and stirring frequently. Don't walk away - they'll toast quickly!. As soon as you smell the walnuts, after 3-4 minutes, remove them from the heat and transfer them to a plate or paper towel to cool.
Make the dressing: In a mason jar, combine all dressing ingredients and shake vigorously.
Combine the salad: In a large bowl the cooked butternut squash and onions, warm quinoa, walnuts and cranberries. Top with apple cider dressing and stir to combine.
Serve warm, at room temperature or chilled.