Step 1

For the squash and sauce: Preheat the oven to 400 degrees F and place a rack in the middle of the oven.

Step 2

Rub 1/2 tablespoon of the olive oil on each cut-side of the squash and sprinkle with salt and pepper. Place the squash cut-side up on a baking sheet and roast until fork tender, 45 minutes to 1 hour.

Step 3

To test for doneness, insert a knife into the squash; it's ready when the knife goes through with little resistance. Cool the squash for at least 10 minutes. Scrape the tines of a fork lengthwise along the flesh of the squash to pull out the long, thin strands.

Step 4

While the squash cooks, make the sauce. Heat the remaining 1 tablespoon oil in a large nonstick saucepan set over medium heat. Add the onions and garlic and cook, stirring occasionally, until the onions are translucent, 3 to 4 minutes. Add the carrots and celery, and cook until the carrots are fork-tender, 3 to 5 minutes. Stir in the crushed tomatoes, diced tomatoes, tomato paste, oregano, red pepper and bay leaf. Cover the pot, reduce the heat to medium-low and simmer for at least 25 minutes (the longer the better), stirring occasionally. Season with salt and pepper.

Step 5

For the meatballs: Combine the ground beef, flour, tamari, tomato paste, salt, pepper, cayenne, garlic and egg in a large bowl. Form about 40 bite-size (1-inch in diameter) meatballs. Place the meatballs in the sauce and simmer until firm to the touch and cooked through, about 15 minutes.

Step 6

Plate the spaghetti squash on serving plates and top with the tomato sauce and meatballs to serve.