Turnng dehydrated tomaotes into tomato paste?

I had read a tip - not sure where - about how instead of buying tomato past in a can, you dehydrate tomatoes, put them through a grinder to make a powder. When a recipe calls for tomato paste, you make a paste with the powdered tomato and water. Has anyone done this before? If so, did it work out good? What type of tomatoes did you use?