Cook the pasta in a large pot of salted boiling water, to al dente (about 10 minutes).
Meanwhile, heat the olive oil in a Dutch oven or large saute' pan over medium heat. Add the garlic and red pepper flakes and cook until just fragrant, about 30 seconds. Stir in the tomato sauce, water, tomato paste, salt, pepper, sugar and butter. Heat, while stirring, until the butter is melted. Slowly stir in the milk, then turn the heat to low. Simmer at low heat for 10 minutes.
Stir the shredded cheese into the soup until melted. Drain the pasta and transfer to a serving bowl. Pour as much of the tomato sauce into the pasta as desired; stir to combine. (I don't like mine extremely soupy, so usually have about 1/3 cup of the sauce leftover.)
Looking for the convenience factor? Double the batch and freeze the rest for later. Heat on the stove top or in the microwave when you're ready for that quick lunch or dinner!