How to Make It
Heat oven to 400° F. Heat the oil in a large saucepan over medium heat. Add the garlic and sun-dried tomatoes. Cook, stirring, for 2 minutes. Add the crushed tomatoes.
Cut up the whole tomatoes in the can with scissors or crush by hand. Add to the saucepan with the vinegar, ½ teaspoon salt, and ¼ teaspoon pepper. Simmer, stirring occasionally, until thickened, 15 to 20 minutes.
Meanwhile, bring a large pot of water to a boil. Add 1 tablespoon salt. Cook the penne for half the package directions’ recommended time.
Add the spinach to the sauce and cook, stirring, until it begins to wilt, about 1 minute. Add the drained pasta and toss to combine.
Place half the pasta mixture in an 8-inch square baking dish and sprinkle with 1 cup of the mozzarella. Top with the remaining pasta and sprinkle with the remaining 1 cup mozzarella and Parmesan.
Place the baking dish on a rimmed baking sheet and bake until bubbling and beginning to brown, 15 to 20 minutes. Serve with the salad (if desired).