Prepare the dressing. Add the vinegar to a large bowl. Slowly add ¼ cup extra virgin olive oil, whisking continuously. Set aside.
Using a fine-mesh strainer, rinse and drain quinoa. Place in a pot with water and a pinch of salt. Bring to a boil over high heat.
Reduce heat, cover, and simmer until the liquid is absorbed (~15 minutes). Look for a white ring that pops out when the quinoa is cooked. Remove from heat and let rest, covered, for 10 minutes. Fluff with a fork and transfer to the bowl with dressing.
While the quinoa is cooking, heat a sauté pan over medium heat. Add remaining oil. Once the oil is shimmering, add the diced butternut squash. Stir occasionally at first, then more frequently as the squash browns, ~10 minutes. Add the diced onion and cook for 5 more minutes, or until the squash is tender and the onion is translucent.
Add butternut squash, onions, and remaining ingredients to the bowl with the slightly cooled quinoa. Using a spatula, fold until well-combined. Add salt and pepper to taste. Enjoy!