Make a second meal out of Three-Cheese Macaroni by transforming it into this hearty casserole.
Preheat oven to 400 degrees. In a large skillet, heat 1 tablespoon olive oil over medium. Add onion and cook until softened, about 8 minutes. Stir in tomatoes with juice and cook until tomatoes are heated through, 2 minutes. Add macaroni and cheese, gently stirring to combine. Remove from heat and stir in sour cream and basil; season with salt. Transfer to a 2-quart baking dish, top with breadcrumbs, and drizzle with 1 tablespoon oil. Bake until sauce is bubbling at edges and breadcrumbs are golden, 20 minutes. Let cool 5 minutes before serving.