Combine the (uncooked) pasta, milk, marinara, and water in a large saucepan. Stir until well combined and then turn heat to high. Bring the contents to a boil. Once boiling, stir in the salt and reduce heat to a simmer. Cook, stirring often, until the pasta is tender and the liquid has mostly absorbed and there is a nice, thick sauce, 12-15 minutes.
Remove from heat and serve and enjoy!
Reheating hack: to reheat this pasta, I like to toss it in a skillet with 1/4 cup of either milk or water over medium heat, stirring, until the pasta is rehydrated and warm and the excess liquid has absorbed.