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Spaghetti Squash with Handmade Lemony Pesto

Spaghetti Squash with Mushrooms and Handmade Lemony Pesto

  • Author: Tessa
  • Total Time: 55 mins
  • Yield: Up to 4 entree servings 1x


There’s a certain sense of satisfaction in making this pesto by hand, not buying it in the store or using a bright, shiny food processor. You control the balance of flavors (use the recipe quantities and go from there) and are guaranteed freshness.


  • 4 lbs. spaghetti squash (2 small or 1 large)
  • 5 T olive oil (see notes)
  • Kosher salt
  • Ground black pepper
  • 12 oz. sliced mushrooms (button, or your favorite variety)
  • 1 large bunch fresh herbs, leaves and tender stems finely chopped (I like parsley or basil)
  • 1 t finely minced garlic (about 1 clove)
  • 1 t lemon zest (from about half a lemon)
  • 1 T lemon juice
  • 1/2 C pine nuts or walnuts, toasted
  • 1/4 C packed finely grated parmesan cheese
  • 1/4 lb. shredded whole milk mozzarella (optional)


  1. After cutting off the stem, halve spaghetti squash lengthwise and use a spoon to scrape out the seeds. Rub a thin coat of olive oil on the exposed flesh and sprinkle moderately with salt and pepper. Turn cut side down in a 9×13 or half sheet pan and add 1 tablespoon water to pan. Roast at 350 degrees (F) for 35 to 45 minutes, until the skin is slightly tender to the touch. Turn squash face up in pan to cool.
  2. While squash bakes and cools, prepare mushrooms and pesto.
  3. Heat medium cast iron or other oven safe skillet over medium on stovetop; add 1 1/2 tablespoons olive oil and heat until shimmering and fluid. Add mushrooms and stir to coat in oil. Cook about 10 minutes, stirring only every 2 or 3 minutes, until tender and liquid has evaporated completely. Leave mushrooms in pan.
  4. To make pesto, combine herbs and 3 tablespoons olive oil in a ramekin or other small bowl. Stir in garlic, lemon zest, and lemon juice. Place nuts in a new freezer bag, lay flat between 2 layers of dish towels, and use rolling pin or canned food item to smash nuts to a near powder. Because you’re crushing the nuts by hand, the mixture won’t be perfectly uniform–a few larger chunks add welcome texture. Add crushed nuts, parmesan cheese, 1/4 teaspoon Kosher salt, and a pinch of ground black pepper to the herb mixture and stir to thoroughly combine, until it resembles a thin paste. Adjust seasoning if necessary.
  5. Working in the pan used for roasting, scrape “noodles” from spaghetti squash skins with a fork and discard skins. If time permits, place noodles in colander in sink and allow to drain for 5 to 10 minutes, or press with the back of a wooden spoon to speed the process. Noodles don’t need to be completely dry, but removing some moisture will make for better leftovers.
  6. Add squash noodles and pesto to pan with mushrooms and stir to combine. Taste and season with salt and pepper, if needed (will depend on the seasoning in pesto). Serve warm as is, or top with grated mozzarella and broil a few minutes to brown cheese (be sure your pan is oven safe!). Be careful handling the hot skillet fresh from the oven.


To make it vegan, substitute nutritional yeast for parmesan in the pesto, or just leave out the cheese. I tested the nutritional yeast version, using a 1 for 1 substitute for the quantity of parmesan, and I could barely taste a difference.

If you’re uncertain about the size bunch of herbs to buy, you’ll need about 3 C of leaves.

Cooking quality olive oil is fine for sauteeing the mushrooms and coating the squash, but consider a higher quality olive oil for a better tasting pesto. Since the most expensive oil on the shelf isn’t always the best, try finding a specialty olive oil or foods store for assistance. My local store also sells online.

Total recipe time is just under one hour. There’s plenty of time for all other prep while the squash cooks.

Pesto recipe yields about a cup. You can easily use it all with the squash, but feel free to go light on pesto and save some for other uses.

  • Prep Time: 55 mins
  • Cuisine: Gluten Free, Vegetarian