Preheat oven to 450 degrees F. Line a large baking sheet with parchment paper.
Carefully split the spaghetti squash in half from top to bottom. See notes above for tips and tricks. Remove the seeds. Oil the insides of the squash with 2 tablespoons of olive oil. Season generously with salt, pepper and the ½ teaspoon garlic powder. Place the squash flesh side down on the baking try and roast for 40-45 minutes. While the squash is roasting start on the bolognese sauce.
In a large skillet melt the butter and remaining 2 tablespoons of olive oil over medium high heat. Add the chopped onion and cook, stirring often for 8 minutes or until the onion begins to soften and turn translucent. Add the minced garlic and cook an additional minute. Next, add the ground beef, breaking up with a wooden spoon. Cook until the beef begins to brown, about 5 minutes. Stir often.
Once the ground beef has browned add the tomato paste, oregano, basil, red pepper flakes and a few grinds of salt and pepper. Turn the heat up to high to 'toast' the tomato paste and herbs, cooking for one minute until fragrant. Turn the heat back down to low and add the marinara sauce and red wine. Gently simmer for 30 minutes stirring often. Adjust seasonings to taste.
Decrease oven temperature to 425 degrees F.
When the squash and bolognese sauce are ready, on the same parchment lined baking sheet used for roasting the squash, dived the sauce between both spaghetti squash boats and top with the mozzarella cheese. Bake in the oven for 20-25 minutes or until the mozzarella begins to bubble and brown.
To serve, use a fork to dig up the spaghetti squash 'noodles' from the flesh of the squash, then spoon the desired amount of bolognese sauce to serve. Top with freshly grated parmesan cheese and ground pepper. ENJOY!