Pre-heat oven to 400 degrees. Line a 9x13" baking sheet with aluminum foil. Set aside.
Cut spaghetti squash in half and remove seeds. Rub cut side of flesh with 1 tsp olive oil, then season with 1 tsp Flavor God seasoning. Place cut side up on lined baking sheet and bake for 40 minutes or until squash can be easily flaked apart with a fork. Set aside to cool.
Add sliced onions to a skillet over medium-high heat and begin to caramelize them, stirring every couple of minutes and lowering heat to medium as they begin to turn brown. Add small amounts of water (1-2 tbsp at a time) to the skillet as needed to reduce sticking and to help steam and soften the onions. Continue cooking down and stirring until onions are caramelized, about 20-30 minutes. Set aside.
Heat 1 tsp olive oil in the skillet over medium high heat. Season chicken with salt and add to hot skillet. Cover and cook 5-7 minutes per side or until cooked through. Set aside and cut into slices when cooled.
Add butter and garlic to the skillet and saute until fragrant. Add remaining sauce ingredients, stirring until they are all combined and sauce is heated through.
Scrape spaghetti squash flesh into a bowl. Pour thawed spinach onto a double layer of paper towel and squeeze out excess water, then add into bowl with spaghetti squash.
Add sauce, caramelized onions, sliced sausage, sliced chicken, and pecorino romano cheese to the bowl. Stir until combined, then transfer to a greased casserole dish (I used an ~11"x7"x2" dish). Top with shredded mozzarella cheese, then bake at 375 degrees for 20-25 minutes or until cheese is melted and golden.