Heat the oven to 400 F. Spread the squash in an even layer on a rimmed baking sheet and toss with 2 teaspoons olive oil, salt and pepper. Ensure that each piece is coated with oil. Put the pan into the oven and roast the squash for 30 minutes, tossing every 10 minutes.

While the squash roasts, caramelize the onions. Heat the remaining 2 teaspoons of olive oil in a large nonstick skillet over medium heat. Add the onions and garlic and stir until they are well-coated with the oil. Add a small pinch of salt and cook for about 5 minutes until they begin to soften. Add the dried sage and stir.

Reduce the heat to medium low and place a lid on the pan, but leave it open just a bit to allow it to slightly vent. Stir frequently to ensure the onions are not burning. The onions will become very fragrant and soft after about 10 more minutes. Add about 1 tablespoon of water and stir. Return the lid to the pan and cook for another 10 minutes to allow the water to steam the onions.

When the squash and onions are done, wrap the tortillas in a damp towel and warm them in the microwave for about 30 seconds.

Scoop the roasted butternut squash into the tortillas, about 1/3 cup each. Top with the onions and Parmesan cheese and dig in!

Notes:
Instead of putting it in tortillas, this can be served as a side dish as well. Just mix the onions into the roasted squash and top with the Parmesan.

I think this would be excellent with sweet potatoes and/or pumpkin in place of the butternut squash. Or just combine all three!