To make tomato powder, you first have to dehydrate the tomatoes. I won't go into the details of how to do that but this link will show you how to dehydrate the tomatoes.
Once the tomatoes are completely dried, just toss them into a blender or we use a single serve blender (like you would use to make smoothies) and grind the tomatoes until they turn into a fine powder. Just store it in a mason jar out of direct sunlight. I know the one I have pictured shows it in a baggie but every time I took a photo of it in the mason jar, it looks so pale and I wanted to show you how vibrant the powder truly was.
Tomato powder can be used in the powder form to thicken soups, sprinkle on salads or hamburgers. To make homemade tomato sauce with tomato powder, use 2/3 cups of tomato powder and 2 cups of water and it will make the same amount as a 15 oz. can you would purchase from the store. To make tomato paste, use 6 T. of tomato powder and 1/2 cup of water to equal a 6 oz. can of tomato paste. If you want to make tomato juice, use 1 c. of tomato powder and 8 c. of water and it will equal a 64 oz. bottle of tomato juice.