This vegetarian main dish is packed with Italian flavors.
Place both whole spaghetti squash in a large stockpot of water. Cover pot, and bring water to a boil. Reduce heat to a simmer, and cook the squash until it is slightly tender when you press it with your fingers, 20 to 30 minutes. Drain. Using a serrated knife, cut the squash in half crosswise. Stand the halves on end, with cut sides up, and set aside to cool 15 minutes.
Heat oven to 450 degrees. Remove the seeds from the squash halves; discard them. Using a teaspoon, scrape the flesh; it will separate into spaghetti-like strands. Transfer the strands to a large mixing bowl, and transfer the shells to a baking pan; set both aside.
Chop 12 of the tomatoes into 1/2-inch pieces, and add to the squash strands. Slice the remaining 4 tomatoes into 1/4-inch-thick rounds, and set aside.
Place the garlic, olive oil, basil leaves, salt, and pepper in the bowl of a food processor. Process until the basil has been very finely chopped, about 2 minutes.
Transfer the basil mixture to the mixing bowl with the squash strands and the tomato pieces; toss with vegetables to combine. Divide the mixture among the reserved squash shells, and top each shell with several tomato slices. Sprinkle 1 1/2 tablespoons Parmesan cheese over each shell.
Transfer the baking pan to the oven, and bake the stuffed squash until the cheese is golden and a metal skewer inserted down into the stuffing comes out hot when held there for 15 seconds, about 30 minutes. Transfer to a wire rack to cool slightly. Garnish with basil sprigs, and serve warm.
If you are on a strict low-fat diet, substitute 2 tablespoons water and 1 teaspoon lemon juice for the olive oil in this recipe; this will reduce the fat to 4 grams per serving.