Pre-heat oven to 200oC.
Cut off stem and then slice squash in half lengthwise. Scoop out seeds. Drizzle with olive oil and roast cut side down for 40-50 minutes.
Once the spaghetti squash is cooked, which you could do the day prior, you can begin preparing the marinara sauce and other ingredients.
Heat olive oil in a medium saucepan. Add onion and garlic. Sauté until soft and translucent.
Then add the tomatoes, Italian herbs, pepper and salt. Cook on medium heat for 10 minutes. Stir occasionally, while preparing the other ingredients and placing them out ready to construct your lasagne.
Once the spaghetti squash is cooled, use a fork to scrape out ‘spaghetti’ and place in a bowl for later use.
Inside the two spaghetti squash ‘boats’, scoop in 1/3 of the marinara sauce. Then top with 1/3 of the spaghetti squash. Then top with half the spinach and feta; spreading it out evenly across the surface. Then add another layer of marinara sauce, then spaghetti squash and the spinach and feta. Cover with the final layer of spaghetti squash and smother in the remaining marinara sauce. Top with Parmesan cheese.
Place in oven to bake for 15-20 minutes, until cheese browns.
Serve with a side salad.