Preheat the oven to 400 degrees.
Brown meat on the stovetop in 1 Tbsp olive oil. Once browned, add the taco seasoning and ¼ C water.
Add tomatoes and onions to the pan and cook for 3-5 more minutes, until the veggies are tender.
Add spaghetti squash to a 9×13 baking dish then top with meat mixture. Top with shredded cheese, and bake for 15 minutes, or until everything is all melted together.
Once the taco bake is removed from the oven and slightly cooled, divide squash casserole into 12 squares using a knife or a spatula and add optional toppings