Preheat your oven to 400°F or 200°C. Place the halved acorn squash on the baking sheet and roast it for 25 to 30 minutes.
Take a saucepan. Sauté onion in it for 5 minutes, then sauté garlic in it for 1 minute.
Then add tomato paste, herbs, black pepper, and nutmeg to the pan. Stir everything well and let it cook for 1 to 2 minutes.
Scoop the roasted squash into the blender. Also, put in the mixture from the pan and the low-sodium broth. Blend everything until it turns smooth.
Pour the paste back into the pan and simmer it for 10 to 15 minutes. Make sure it's on a medium flame.
Lastly, adjust seasonings if needed and let the sauce cool down.