Preheat oven to 400 degrees F.
Slice the acorn squash in half, from the tip to the bottom. Using a spoon, scoop out the seeds and discard. Place the 2 pieces on a baking sheet. Divide the butter in half and place each pad of butter in the center of the squash. Season with salt and pepper. Add 1 cup of water to the bottom of the baking dish so the bottom of the squash doesn't burn. Place the squash in the oven and let it roast for 60 - 70 minutes.
Remove squash from the oven once the insides of the squash is fork tender.
In a large skillet add the olive oil over medium high heat. Saute the onion for about 7 minutes until they are translucent. Add the garlic and saute for 1 minute more. Add the scallions and stir until just together. Remove skillet from heat.
Season the onion mixture with salt and pepper. Add the cooked quinoa, shredded Parmesan cheese and lemon juice. Toss together and adjust seasoning as needed.
Place half of the quinoa mixture in each of the squash cavities. Sprinkle the shredded hard goat cheese on top. Place the squash back into the oven for about 5 minutes, just until the goat cheese cheese slightly melts.
Remove from oven and serve immediately.