How can I keep meringue pie-topping from falling? Nothin' better on a hot summer afternoon than a slice of cold pie... And nothin' says "summer" like a great big fluffy meringue topping over that slab of rhubarb/lemon/banana custard. 

Unfortunately, mine haven't been turning out that way. They bake up nicely, but fall within a half hour of baking. 

I whip egg whites mixed with 1/8 tsp cream of tartar (per egg) until they reach soft peaks, then mix in 1 tablespoon of sugar (per egg) while continuing to beat until it gets stiff - then spread over the hot pie filling and bake for 10-15 minutes at 400F. Topping doubles in size, then falls as it cools, ending somewhat less impressive than it started.

Any suggestions?
Ironically, it could be precisely because you're trying to enjoy the meringue on a hot day that is causing it to deflate so quickly. Meringue are extremely sensitive to moisture, and a humid day can wreck your meringue's volume. It's best to make meringue on a dry day. 

However, there are a few things you can do to achieve better stability:


Use fresher eggs. 
Fats are the enemy. Make sure you have zero egg yolk in the mixture. Also, avoid hand contact, as your oils can rub off. 
Make sure the sugar is fully dissolved, because otherwise it attracts moisture. 


Good luck!