Discover the Ultimate Pesto Spaghetti Squash Recipe!

Preheat the oven to 400 degrees F (200 degrees C). Grease a baking sheet.

Place squash skin-side down on prepared baking sheet. Bake until cooked through, about 1 hour. Remove from oven; cool for 10 minutes. Once squash is cool enough to handle, scrape flesh into string-like strands with a fork. Place in a bowl and set aside.

Melt 1 tablespoon of butter in a large skillet over medium-high heat. Add onion; cook and stir until onion begins to turn translucent. Stir in kale and mushrooms; reduce heat to medium low.

Stir in squash, remaining 2 tablespoons butter, garlic salt, Italian seasoning, and red pepper flakes; cook for 2 minutes. Remove from stove and place squash mixture in a large bowl.

Stir olive oil and pesto into the squash mixture. Slowly add grated Parmesan cheese, stirring until evenly mixed.