This Spaghetti Bolognese Casserole is a great one pan meal for feeding a crowd. Spaghetti squash is used in place of traditional spaghetti to make this Whole30 and Paleo and it's tossed in a rich beef tomato sauce and then baked in the oven.
Preheat the oven to 200 degrees Celsius (400 degrees Fahrenheit)
Heat the oil in a skillet and add in the diced onion and garlic. Saute for 4-5 minutes until the onion begins to soften and then add in the mushrooms and cook for 2 minutes.
Add in the ground beef and using a wooden spoon break it up into a crumbly texture. Once the beef is no longer pink in colour, stir in the canned tomatoes and oregano and let simmer for 5-10 minutes until the sauce has thickened.
In a bowl stir together the spaghetti squash and egg before adding in the spinach and sauce and stir until everything is well mixed. Transfer everything to a cast iron skillet or oven proof dish. Place the sliced tomatoes over the top of the casserole and then cover with tin foil, and bake for 25 minutes, removing the tin foil and allowing it to bake uncovered for an additional 10 minutes.