Melt the butter in a skillet on medium heat. Add the chopped tomatoes, basil and salt.
Stir constantly for the first 5 minutes as the tomatoes boil down into a sauce
After 5 minutes on medium heat, turn the stove down to medium low and simmer for another 15 minutes. Stir frequently and mash up the tomatoes with your spoon as you do. When the sauce is the consistency you want, remove the skillet from the heat.
Boil the pasta as directed on the package. Time it as closely as possible so it will be done when the sauce is.
If you want to add cheese to the sauce, remove it from the heat before you stir it in.
Scoop the pasta from the water and put it into the skillet with the sauce. Some of the pasta water will come over into the skillet with the pasta. That is perfect. Pasta water is an ingredient in a sauce like this. Mix the pasta into the sauce and let sit off the heat for about 3 minutes to let the flavors blend together with the pasta.