Preheat the oven to 400 degrees F. Slice the spaghetti squash in half lengthwise. Scrape out the seeds. Spray or drizzle the cut side with olive oil and season all over with salt and pepper. Roast the squash cut-side down for 30 minutes, or until tender.
While the squash roasts, make the beef. Place the beef in a skillet over medium heat. Season all over with salt and pepper. Cook until browned, breaking it apart into small crumbles. Stir in the ketchup and mustard until combined. Turn off the heat and add in a sprinkle of cheese - just an ounce or two. Let the beef cool slightly.
Use a fork to scrape up the strands of the spaghetti squash. This just loosens it so it’s easier to eat! Top each squash with a few spoonfuls of the ground beef (or as much as you want!) and the shredded cheese. Drizzle with the house sauce.
Stick the squash back in the oven so the cheese can melt, about 5 to 10 minutes.
Remove from the oven and top with all the toppings! More house sauce, lettuce, tomato, pickles and pickled onions. YUM.