Preheat your oven to 400°F (205°C) and position the oven rack in the middle.

Slice the spaghetti squash in half lengthwise and scoop out the seeds. Brush the insides with olive oil and place cut-side down on a baking sheet. Roast for 35–40 minutes until fork-tender.

Heat a drizzle of olive oil in a skillet over medium heat. Sauté diced onions for about 5 minutes until soft, then add minced garlic and sauté for an additional minute.

Once the spaghetti squash is cool, shred the flesh into strands using a fork.

In a large mixing bowl, combine shredded squash, sautéed onions and garlic, Greek yogurt, 1 cup of shredded cheddar, salt, pepper, and any optional spices. Mix well.

Transfer the mixture to a greased casserole dish and sprinkle remaining cheese on top.

Bake in the preheated oven at 375°F (190°C) for 20–25 minutes until golden brown and bubbly.

Let the casserole cool slightly before serving as a delicious side or hearty main course.