Spaghetti Squash with Mushroom Onion Sauce

by Amy Renee
Spaghetti Squash with Mushroom Onion Sauce

This is the perfect meal for when you want something healthy but still filling and delicious. Throw in some black beans and trade out the 21 seasoning salute for some chili powder and cumin for a southwestern flare. Yum! I love squash. Butternut squash, acorn, zucchini and summer squash, kabocha, delicata…it’s all so delicious.

A simple meal full of superfoods

I wrote about the health benefits of mushrooms and garlic in my last blog post here. Spaghetti squash is a great source of niacin, vitamin B6, pantothenic acid, potassium and manganese, and an excellent source of fiber and vitamin C. Onions are full of phytonutrients that ward off infection and inflammation in the body. So pretty much every component of this meal benefits your health and fights off disease while being low in calories and fat at the same time.

This was one of the simplest meals I’ve prepared in a long, long time. And soooooo delicious! You might want to double the recipe though, because you’re definitely going to want seconds!

Squash is very inexpensive, easy to cook and so versatile you can enjoy it about a million different ways. I like to bake up a few spaghetti or butternut squashes at the same time so that I have extra in the fridge for an easy throw together meal in a hurry. It’s even good cold!

So when hunger struck and my fridge was pretty much empty except for some cremini mushrooms I threw together this recipe. I was impressed by how delicious it was. My tummy was quite pleased as well.


Prep Time: 15 minutes     Cook Time: 1 hour     Total Time: 1 hour 15 minutes     Serves: 4 servings

  • 2 medium spaghetti squash
  • 1 large sweet onion, sliced into half moons
  • 8 ounces mushrooms, sliced
  • 4 cloves garlic, minced
  • 2 teaspoons chopped fresh rosemary
  • 2 teaspoons Trader Joe’s 21 seasoning salute
  • ¼ teaspoon salt
  • ½ teaspoon pepper
  • ½ cup low-sodium vegetable broth
  • 1 tablespoon arrowroot or cornstarch dissolved in about 2 to 3 tablespoons cold water
  1. Preheat oven to 375°F. Line a baking sheet with foil or parchment. Cut spaghetti squashes in half lengthwise and scoop out seeds and loose stringy pulp from the center cavity. Place halves cut-side-down the prepared baking sheet and roast until the squash is soft when you press down on it, 50 to 60 minutes total. Flip it over and try to scrape up the spaghetti-like flesh, to check if it is done. If it is loose and stringy it is done. It shouldn’t be watery. If it doesn’t come up easily, return to the oven and check again in ten minutes.
  2. While the squash cooks you can prep the onions, mushrooms, garlic and rosemary. This should only take ten minutes at the most, so just set the cutting board in the fridge or off to the side until you are ready to start cooking.
  3. During the last 25 minutes or so of cooking time for the squash, spray a skillet with organic canola oil cooking spray and heat over medium heat. Add onion and cook, stirring occasionally until the onion turns golden brown, about 18 minutes. Reduce heat to medium-low and continue cooking, stirring occasionally until the onions are soft and dark golden brown, about 4 to 5 minutes more.
  4. Place the cornstarch in a small jar and add just enough cold water to dissolve it. Tighten the lid and shake until it is completely dissolve and set aside.
  5. Transfer the onions from the pan to a bowl and set aside. Add the mushrooms to the pan and increase the heat to medium-high. Cook, stirring often until the mushrooms release their juices and the juices evaporate and a brown fond develops on the bottom of the skillet, 4 to 6 minutes. Add the garlic, rosemary, 21 seasoning salute, salt and pepper and stir, cooking about one minute longer. Add the onions back to the pan with the broth and bring to a boil. Whisk in the dissolved cornstarch and cook until the sauce has thickened, 2 to 3 minutes.
  6. Scrape spaghetti squash up from the shell with a fork. Serve squash topped with the sauce.

If using cornstarch try to find organic or non-GMO cornstarch.

This is delicious on it’s own for an ultra light meal (if you’re just not that hungry or plan to eat in just a couple of hours), but you could easily add lentils, hummus or any kind of beans for a perfectly balanced meal.

Nutrition Information
Serving size: ¼ recipe Calories: 75 Fat: 0.6 Saturated fat: 0 Trans fat: 0 Carbohydrates: 14 Sugar: 4.9 Sodium: 200 Fiber: 2.4 Protein: 4 Cholesterol: 0

If you’re a garlic lover like me feel free to throw in a few extra cloves. I made mine with five huge garlic cloves, and I only made half the recipe so as you could imagine my entire apartment smelled like a giant clove of garlic. Ha!

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