Spaghetti Squash Casserole

This simple spaghetti squash casserole recipe harnesses the intense savory flavors of tomato paste, onion powder and sharp cheddar cheese, to make an easy, healthy vegetarian meal that will satisfy your comfort food cravings. 

Spaghetti squash works beautifully in a casserole.  I say that with a mixture of excitement and surprise because until recently I had never used spaghetti squash other than as a healthy substitute for pasta, topped with my favorite turkey ragu.

This recipe came about by accident while I was working on a post about the best way to cook spaghetti squash. I had a LOT of cooked spaghetti squash on hand and, much as I love my turkey ragu, I didn't want it for dinner two nights in a row. I threw the spaghetti squash together with an onion, some garlic, a few dried spices, a can of tomato paste and a bag of shredded cheddar, baked it all together and voila - spaghetti squash casserole! I never intended this for the blog but we loved it so much, I just had to share.

If you like baked ziti and lasagna, you'll love this dish. The combination of tender spaghetti squash noodles, rich tomato sauce and melted cheddar cheese is incredibly delicious and comforting, plus there's the added benefit that this comforting casserole is made with a nutritious vegetable instead of pasta. 

This is an easy recipe and it uses common ingredients that you probably already have on hand - other than the spaghetti squash. 

Spaghetti Squash Casserole

Here's how to make it - step by step with photos. (See the printable recipe card below, for exact amounts and detailed instructions.)

Start by cooking the spaghetti squash. You can find my recommended technique for cutting and roasting spaghetti squash in this post -  how to cook spaghetti squash. 

Put 4 cups of the cooked spaghetti squash into a large mixing bowl and set it aside while you make the sauce. 

For this simple sauce, start by sautéing a chopped onion, a few chopped garlic cloves and a pinch of red pepper flakes. When the onion is soft and starting to brown, add a can of tomato paste and cook it for a minute or so, stirring with a wooden spoon, until its color deepens.

Tomato paste is one of my favorite pantry ingredients. It has s deeply savory, umami flavor. This way of cooking and caramelizing tomato paste further intensifies its wonderful flavor. I love using this technique to make a quick flavorful tomato sauce for rice, pasta or spaghetti squash.

Add the tomato paste mixture to the bowl with the squash, along with the onion powder, dried basil, salt, pepper and half of the shredded cheddar cheese. Stir well. 

Onion powder is another one of my favorite culinary secret weapons for adding fantastic flavor to a dish quickly and easily. It has a sweet and savory oniony taste that's different from fresh onions and wonderful in its own right. I use it liberally - it's hard to overdo onion powder - it's so good.

Sharp cheddar cheese is another fantastic ingredient for adding rich umami (savory) flavor to a dish - and even more so when it's hot and melted into a casserole!

Transfer the mixture to a casserole dish, sprinkle the rest of the cheese on top, and bake it for 40 minutes.

How to serve it

Serve this casserole hot, with a salad on the side. It goes beautifully with this Italian tricolore salad. Or if you prefer, make the delicious lemon-dijon vinaigrette from the tricolore recipe, and use it to dress whatever lettuces you have on hand. 

If you try this spaghetti squash casserole recipe, I hope you'll come back to leave a star rating and a comment. I'd love to know what you think.

Spaghetti Squash Casserole

---

★★★★★

5 from 2 reviews

• Author: Lisa
• Total Time: 1 hour 20 minutes
• Yield: 4 generous main dish servings 1x
• Diet: Vegetarian

Print Recipe

Description

This easy Italian-style spaghetti squash casserole recipe is perfect for the weeknight dinner rotation - a healthy vegetarian meal that satisfies.

---

Ingredients

Units USM Scale 1x2x3x

Equipment: a 2-quart casserole

• 4 cups cooked spaghetti squash from 1 large - 3-lb. squash. Here's how to cook spaghetti squash
• 2 tablespoon olive oil, divided
• 1 large yellow onion, chopped
• 3 large garlic cloves, minced or passed through a garlic press
• 1 or 2 pinches of crushed red pepper flakes
• A 6-ounce can of tomato paste
• 1 teaspoon dried basil
• 2 teaspoons onion powder
• ½ teaspoon Kosher salt
• Several grinds of black pepper
• 1 cup shredded extra sharp cheddar cheese, divided

Cook Mode Prevent your screen from going dark

---

Instructions

preheat oven to 375ºF/190ºC

1. Put the cooked spaghetti squash into a large mixing bowl and set aside.
2. Heat 1 tablespoon of the oil in a medium saucepan or in a skillet over medium heat and sauté the onion, garlic and red pepper flakes, stirring occasionally, until the onion is soft and starting to brown, about 5 minutes. Add the second tablespoon of oil and the tomato paste and cook for 1 minute, stirring constantly with a wooden spoon. Tomato paste will caramelize and darken in color, and some may stick to the pan. Remove pan from heat, add a tablespoon of water, and scrape the pan with a wooden spoon to release any stuck bits, and then transfer the tomato paste mixture to the bowl with the squash.
3. Add the basil, onion powder, salt, pepper and half the cheese. Mix thoroughly, transfer to the casserole, top with remaining cheese, and bake for 40 minutes. Serve hot, with a salad on the side, if you like.

• Prep Time: 10 min
• Roasting the spaghetti squash: 30 min
• Cook Time: 40 min
• Category: Casserole
• Method: Bake
• Cuisine: Italian-style

Keywords: healthy spaghetti squash casserole, spaghetti squash casserole with tomatoes and cheese