I have had good luck with a basic dehydrator. The unit consists of a couple of stacking racks with a fan at the bottom for air circulation and a heater to control temperature. I have seen some good plans for solar dryers, but haven’t made one myself. These are little more than screens that you cover to keep the bugs out and set out in the sun.
I have also had good luck with “tomato leather”. Basically you make a puree in a blender, put it in a pot and bring it to a boil, let sit overnight to separate the solids from the liquid, us a turkey baster to suck of the clear liquid off the top (save this and use it as a stock), pour the solids on to a tray in the dehydrator and dry. What you wind up with is the tomato equivilant of a “fruit roll up”. Re-hydrate in oil to use anywhere tomato paste is called for.
Heck. around these parts, all you need do to dry a tomato these days is hold it out the window for a few minutes…