Step 1

Preheat the oven to 450°F with a rack in the center. Heat the oil in a large ovenproof skillet over medium heat until shimmering, about 2 minutes. Add the garlic and cook, stirring, until softened but not browned, 1 to 2 minutes. Add the tomato paste and cook, stirring, until it darkens slightly, 1 to 2 minutes. Add the red pepper flakes, crushed tomatoes, basil sprigs, sugar, and 1 cup water. Season with the salt and black pepper and increase the heat slightly to bring to a boil.

Step 2

Gently separate any frozen ravioli stuck together without tearing. Any that resist will separate during cooking. Add the ravioli to the skillet and cook over medium heat, stirring gently, until the sauce is very thick and the ravioli are just tender, about 15 minutes.

Step 3

Spoon half of the ravioli and sauce into a bowl. Arrange the ravioli in the skillet in an even layer and sprinkle with half of the mozzarella. Arrange the remaining ravioli on top and sprinkle with the Parmesan and remaining mozzarella.

Step 4

Bake until bubbling and the cheese is lightly browned, 10 to 12 minutes. Scatter the basil leaves on top and let rest for 10 minutes before serving.