Chop the tip and tail off the acorn squash, then cut it in half length-wise. Scoop out the seeds and discard them (or you can roast them like pumpkin seeds--they're delicious!).
Drizzle the squash flesh with 1 tablespoon of olive oil and sprinkle with salt and cinnamon. Place both squash halves on a baking sheet, cut-side down. Roast the acorn squash for 45 to 50 minutes, or until the flesh is very soft. Use a spoon to remove the squash flesh from the skin; discard the skin.
Heat the remaining olive oil in a skillet over medium heat. Add the chopped onion and sauté until browned, about 15 minutes. Add the garlic and sauté an additional 2 minutes. Remove from heat.
Add the squash, sautéed onion and garlic, almond milk, and vegetable broth to a blender and blend until completely smooth. Season to taste with salt and pepper and serve with sour cream or plain Greek yogurt, if desired.
Notes
If you have an immersion blender, you can cook the onion and garlic in a Dutch oven, then add the remaining ingredients and blend directly in the pot.
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