Dot the top with the pieces of butter, distributing them evenly over the macaroni and tomatoes so they melt down into everything as it cooks.
Cover the slow cooker with the lid and cook on LOW for 1 1/2 to 2 1/2 hours, stirring once about halfway through. The exact time will depend on your slow cooker and how soft you like your pasta. Start checking around the 1 1/2-hour mark.
When the macaroni is tender and the tomatoes look thick and saucy, give everything a good stir to coat the pasta in the buttery tomato juices. Taste and add a pinch of salt and pepper if you like, keeping in mind the recipe is meant to be very simple and mild.
Serve warm straight from the slow cooker. The mixture will thicken a bit as it sits, and the macaroni will be soft and plump, just like those classic school-lunch style bowls many of us grew up with.
Variations & Tips
If you have picky eaters, you can gently mash the stewed tomatoes more before adding the macaroni so there are fewer big chunks; the sauce will feel smoother but still taste the same. For families who like a little extra richness, stir in an extra tablespoon or two of butter right before serving. If you want a cheesier version, keep a small bowl of shredded cheddar or Parmesan at the table so everyone can add their own without changing the base recipe. To stretch the meal, you can serve the macaroni and tomatoes over toasted bread or garlic toast, almost like a Midwest-style open-faced comfort dish. For a slightly firmer pasta texture, check the slow cooker earlier and switch to WARM once the macaroni is just tender; slow cookers all run a little differently, so the first time you make this, keep an eye on it. Leftovers reheat well with a splash of water or a tiny bit of butter stirred in to loosen the sauce.
