Carefully wash and dry your tomatoes. Cut them in half lengthwise. If you decide to remove the seeds try not to remove the pulp. Use a spoon or your fingers to scoop out the seeds. To shorten the overall drying time, cut a slit in the sides of the tomatoes to facilitate air flow.
Place the halves skin side down on a framed plastic screen. Spread them out so that none are touching. You can salt them at this time for a little more flavor. The salt will also help draw liquid out of the fruit faster. Use a cheesecloth cover over the screen to protect the tomatoes from insects. Make sure to raise the cheesecloth off the tomatoes slightly. Place the screen outside in the sun. Raise the frame up off the ground so that air can flow freely above and below the fruit. It will take at minimum a few days of sunshine to properly dry the tomatoes. Make sure to bring the tomatoes inside when the sun goes down.
When your tomatoes have fully dried, they will have a dark red color or a darker, more intense color than they had originally. They should feel dry and pliable to the touch; they should not be hard and brittle, nor should they feel at all moist.
To Oven Dry:
If your area doesn’t have the sun for sun-dried tomatoes, than over drying will work fine. Using uniform tomatoes sizes will simplify your results. Preheat oven to 200F or the lowest setting on a gas oven. Prepare your tomatoes as above. Instead of cheesecloth, place them on cake racks or a perforated pizza pan. Put the pans directly on the oven racks. You can also cover the oven racks with aluminum foil, just punch small holes in the foil for air circulation. Bake at 200º F for 6 to 12 hours until the tomatoes are fully dried. Check on them regularly and make sure to remove any that are done.