Preheat the oven to 425F (220C) and line a sheet pan with parchment paper. Toss the squash, onion and garlic with aquafaba or water and a pinch of salt if desired. Spread in a single layer onto the sheet pan and roast for 25-30 minutes, flipping once halfway through, until easily pierced with a fork.
While the squash is roasting, cook the macaroni noodles until al dente. Drain, rinse and add back to the cooking pot.
When the squash has finished roasting add the entire pan to a blender along with the cashews, water and salt to taste. Blend until smooth and creamy, adding a little more water, a tablespoon at a time, to create a smooth pourable sauce.
Pour half of the sauce over the cooked noodles and stir to combine. Turn the heat on to medium and add more sauce to the noodles to reach desired consistency, gently stirring to coat the noodles and warm through. Enjoy immediately.
Notes
*Frozen squash can be used for this recipe and will make this recipe even quicker to prepare. No need to thaw frozen squash, just proceed as directed in the recipe. **Nut-Free Option: Replace cashews with sunflower or pumpkin seeds, or simply omit. The sauce will be less creamy if you omit them, but is still very delicious!Make Ahead: The cheese sauce can be made up to 3 days ahead of time and stored in an airtight container in the fridge. The sauce will thicken up as it sits in the fridge. When ready to use, add the sauce back to the blender and blend with a little hot water to loosen the sauce and make it pourable again. Pour over noodles and heat through as directed.Leftover Cheese Sauce: Use any leftover cheese sauce as a dip for veggies or chips, or pour over roasted potatoes for easy potato nachos.