Yes you can dry fruits and vegetables in a oven. Tomatoes have to be washed and sliced to 1/2-inch slices; cherries - washed and pitted. Spread items out on baking racks or cookie sheets lined with cheesecloth. Set your oven at 140%u02DAF - 150%u02DAF and place items inside leaving the oven door ajar for circulation.  
 
While it is possible to dry fruits and vegetables in this manner it is not the best way. Fruit must be thoroughly dehydrated in order to store without fear of mold and bacteria growth. Tomatoes with their high water content can take up to 24 hours to dehydrate. A better method is to purchase a home dehydrator - it uses less energy, you can fit much more in one batch and you do not need to worry about fluctuating temperatures that can result in burning.
 
Good luck with your harvest,
Christine