Preheat the oven to 375°F. Grease a 9x13-inch baking dish.
Cook the cheese ravioli in a large pot of salted water according to the package instructions until al dente. Drain the ravioli and set aside.
1 (18-ounce) package refrigerated cheese ravioli
In a large skillet, cook the diced bacon over medium heat until crispy. Remove the bacon with a slotted spoon and set aside on a paper towel-lined plate.
6 slices bacon
In the same skillet with the bacon fat, add the diced onion and cook until softened and translucent, about 5 minutes.
½ large onion
Add the minced garlic to the skillet and cook until fragrant, about 1 minute.
3 cloves garlic
Sprinkle the flour over the onion and garlic mixture, stirring to combine. Cook for 1-2 minutes to remove the raw flour taste.
2 tablespoons all-purpose flour
Gradually whisk in the heavy cream, stirring constantly to prevent lumps from forming. Simmer the sauce for 5 minutes or until it thickens slightly.
2 cups heavy cream
Remove the skillet from the heat and stir in the grated Parmesan cheese, salt, black pepper, and ground nutmeg until well combined.
½ cup freshly grated Parmesan cheese, ½ teaspoon salt, ¼ teaspoon black pepper, ¼ teaspoon ground nutmeg
Add the cooked bacon and cooked ravioli to the skillet with the cream sauce, stirring gently to coat the ravioli evenly.
Transfer the ravioli mixture to the prepared baking dish, spreading it out in an even layer.
In a small bowl, combine the shredded mozzarella and Asiago cheeses. Sprinkle the cheese blend evenly over the top of the ravioli.
1 cup shredded mozzarella cheese, ½ cup shredded Asiago cheese
Bake the Ravioli Carbonara for 20-25 minutes, or until the cheese is melted and bubbly and the edges are lightly browned.
Remove the baking dish from the oven and let the ravioli cool for 5 minutes before serving.