Each summer day I am asked about my sauce, which is simple, no removal of the skins, or fancy techniques like using a meat grinder. I make my sauce by deploying straight up flavors, no tricks just technique.
Plant cells have plastids http://en.wikipedia.org/wiki and plastid like mitochondria have their own DNA. Plastids of other colors, which give leaves their fall colors and flowers and fruits their many hues.
Now when it comes to my sauce think pink, no think red but it is more and more rare that a supermarket tomato is picked ripe. Often they are produced in greenhouses and picked while still green, transported, and when close to being placed for sale, treated with ethylene to trigger the ripening process.
This artificial ripening is done by the fruit without the extra energy from the plant resulting in only a fraction of what the sugar and aroma compound production could have been. So choose the right tomatoes and avoid the larger types, those that look red but are gassed and suffer from a genetic mutation.
Those pretty tomatoes we get at the supermarket have a genetic mutation causing them to have the desired uniform color but which also lessens the formation of those sugar producing chloroplasts SIGLK2.
Making the sauce: http://mesubim.com/2014/07/19/tomato-sauce-extra
Rules of thumb; 1. no heat prior to masticating the tomatoes, 2. never large size tomatoes and 3, do not go fast on reducing the concentrate but not too slowly or you get marmalade. The photos are the three stages of cooking.