Preheat your oven to 350°F (175°C) and lightly grease a baking sheet.
Place the spaghetti squash halves, cut sides down, on the prepared baking sheet.
Bake them in the oven until they become tender and can be easily pricked with a fork, which usually takes about 30 to 35 minutes.
Allow them to cool for approximately 20 minutes.
While the squash is cooling, heat the olive oil in a large skillet over medium heat.
Add the chopped onion and cook, stirring occasionally, until it becomes tender, which should take about 5 minutes.
Then, add the minced garlic and continue to cook, stirring until it becomes fragrant, about 2 to 3 minutes.
Add the diced tomatoes and cook for an additional 2 minutes before removing the skillet from the heat.
Use a fork to remove the spaghetti squash pulp from the shell, and then stir it into the tomato mixture.
Add the crumbled feta cheese, chopped olives, basil, and ¼ cup of pine nuts, and toss everything to combine.
Just before serving, sprinkle the remaining ¼ cup of pine nuts over the dish.
Enjoy your delicious Baked Spaghetti Squash with Tomato, Feta, and Olives!