I saw a recipe that employed Tomato Flour - how do you turn tomatoes into flour?
I don't think you'd be able to produce the same result at home. Even if the tomatoes could be dehydrated to the point where they are crisp enough to be ground, I don't think you could pulverize them fine enough very easily. Even if it is possible, the trouble wouldn't outweigh simply purchasing the commercial product.
I do this at home frequently; start by thinly slicing your tomato (roma tomatoes work best, because they're much meatier) and drying. You can do this using a food dehydrator, or in an open oven with low heat. This will take 5-10 hours, depending upon your tomatoes.
After your tomato slices are dried COMPLETELY, place them on a cookie sheet and freeze them. This will remove any remaining moisture.
Take your frozen and dried tomato slices and put small batches in a coffee grinder until they are powdered. If you want to ensure that there are no flakes, sift the powder through a flour sifter.
Hope this helps!