I make homemade tomato sauce, but you can also use a store-bought variety
Undercooking the jumbo pasta shells just enough before stuffing guarantees they hold their shape under a heavy dairy filling without tearing or turning to mush during the final bake. Boiling jumbo pasta requires careful attention to the timer, specifically pulling the shells at least two minutes before the package directions indicate for al dente, because residual heat and moisture from the ricotta and tomato sauce will continue softening the starch inside the 9x13 inch baking pan. Whisking fresh ricotta, cubed mozzarella, and Parmigiano-Reggiano together before filling creates a cohesive dairy matrix that stays anchored inside each cavity rather than leaking out into the bottom of the dish during the twenty-minute bake at 350 degrees Fahrenheit. Spreading a thin layer of tomato sauce across the base of the pan acts as a protective moisture barrier, preventing the pasta bottoms from scorching while the top develops a browned, bubbling crust from the remaining hard cheese. Swapping homemade tomato sauce for a store-bought jar works entirely fine, though commercial varieties often contain added sugar and sodium that will noticeably alter the salinity and flavor balance of the final dish. Allowing the filled shells to rest briefly after baking lets the melted mozzarella and ricotta set up, making individual portions easier to transfer to plates cleanly.