Heat the oven to 400°F. Place the acorn squash halves cut-side up on a baking sheet, brush with 1 tablespoon olive oil, and sprinkle with half the salt and pepper. Roast for 35-40 minutes until the flesh is tender when pierced with a fork.

While the squash roasts, combine the quinoa and vegetable broth in a medium saucepan. Bring to a boil, then reduce to low, cover, and simmer for 15 minutes until the liquid is absorbed. Remove from heat and let it sit covered for 5 minutes.

Heat the remaining tablespoon of olive oil in a skillet over medium heat. Add the diced onion and cook for 4-5 minutes until softened. Stir in the garlic and dried sage and cook for 1 minute more.

Add the dried cranberries and baby spinach to the skillet. Cook for 2 minutes until the spinach wilts. Fluff the quinoa with a fork and stir it into the skillet mixture along with the remaining salt and pepper.

Remove the roasted squash from the oven. Spoon the quinoa filling evenly into each half, packing it lightly.