Preheat the oven to 400 degrees Fahrenheit. Carefully cut the spaghetti squash in half lengthwise and discard the seeds and membranes.

Place the squash halves in a baking dish. Bake squash for 50-60 minutes or until just fork tender. Let cool for 10 minutes, then use a fork to loosen and shred the squash.

Meanwhile, heat a medium skillet over medium heat. Add the beef and cook, stirring and breaking up the beef, until cooked through and browned, about 7-10 minutes. Strain any excess grease from the pan, then add the marinara sauce and simmer for another 2-3 minutes. Taste and season with salt and pepper to taste.

Mix the ricotta with the Italian seasoning, a pinch of salt and pepper, Parmesan cheese, and 1 cup shredded mozzarella.

Pour about half of the marinara sauce mixture over the spaghetti squash halves, and use a fork to stir the sauce with the shredded squash. Spread the ricotta mixture on top, then the rest of the marinara sauce. Top with remaining ½ cup mozzarella cheese.

Transfer to the oven and bake for another 10-20 minutes or until the cheese is melted and browned in some spots. Broil on high for 2-3 minutes if desired for further browning. Remove from the oven and let cool for 5 minutes before serving.