At this time of year I am processing lots of tomatoes grown in the garden. I roast them and take the skins off before making them into passata or bolognaise sauce. I hate waste and used to throw the skins away, but now I dehydrate them and turn them into free tomato powder. This is great for adding taste to stews, soups, or for making cuppa soups for a day out in the winter (taking a flask of water and adding pasta and dried veg to the mixture).
I personally dry mine in my conservatory under muslin and on a silicone baking sheet, but you could use a dehydrator, an oven, or even the back shelf of a car to dehydrate (as I used to do). Sometimes I will put them out in the sun on a hot, windless day. The skins want to snap and be brittle and not bendy at all or else they will go mouldy. I save them in jars and then grind a lot together.
I grind mine up in a coffee bean grinder and then brush the powder out with a silicone baking brush. I found that my food processor did not grind them well, but it is old and not a good one. I then store them in a dry, recycled glass jar in the cupboard. This is my third jar this season that I have made.
Don’t you just love free things made from waste? Saving on waste, and finding ways to use what I have already, has probably been the biggest help to me in saving money on food.