Thanks for the idea of using lemons to make lemon powder!
We have a lemon tree in the backyard and the only other thing we've done is freeze lemon slices (for year round use) or make Lemoncello Liqueur.
I've used a store-bought spice blend of lemon and pepper (powdered) to season portabella mushrooms and zucchini prior to grilling. Now I'm inclined to make my own blends using our own lemons. :)