How to Make It
Divide the oil between 2 large saucepans and heat over medium heat. Divide the garlic and sun-dried tomatoes between the saucepans and cook, stirring, for 2 minutes. Divide the crushed tomatoes between the saucepans.
Break up the whole tomatoes by cutting them up with scissors (while in the can) or by crushing them with your hands. Divide the tomatoes and vinegar between the saucepans; season each with 1 teaspoon salt and ½ teaspoon pepper. Simmer, stirring occasionally, until thickened, 20 to 25 minutes.
Meanwhile, bring 2 large pots of water to a boil; add 1 tablespoon salt to each. Divide the pasta between the pots; cook for half the recommended time on the package directions (the pasta will continue to cook when it is baked). Drain the pasta; return it to the pots.
Divide the spinach between the saucepans of sauce and cook, stirring, until the spinach begins to wilt, about 1 minute. Pour a saucepan of tomato sauce into each of the pasta pots and toss to combine.
Divide one of the pots of the pasta mixture among four 8-inch square baking dishes (the dishes will be halfway full). Sprinkle each with 1 cup of the mozzarella. Dividing evenly among the dishes, top with the remaining pot of pasta mixture. Sprinkle each with 1 cup of the remaining mozzarella and ¼ cup of the Parmesan.
To eat tonight: Bake the pasta on a rimmed baking sheet at 400° F until bubbling and beginning to brown, 15 to 20 minutes.
To freeze and cook later: Freeze the unbaked pasta, tightly sealed, for up to 3 months. To cook, thaw the pasta and bake, uncovered, on a rimmed baking sheet at 400° F until heated through, bubbling, and beginning to brown, 25 to 30 minutes.