Get yourself a dehydrator if you want to make powders. They do a better job than the sun unless you live in the tropics. I don’t get a drop of rain between mid May and mid September, the temperature never drops out of the 80’s and I still need a dehydrator for final drying.
I have a pretty nice one! I got it to dehydrate tuna for backpacking trips, but I’ve used it for tomatoes.