Yummly is a site where you can search for recipes. You can find many cupcake recipes, if you can't find them here on Cupcakes Take The Cake. Anyway, on their blog, there's a blog post on baking tips in high altitude.
No denying the facts: high altitude + regular (aka “sea level”) recipe = one crumbly, dry cake. It’s all about air pressure. The higher up you go, the less air pressure, so the faster water evaporates, and the faster things bake. Make adjustments to the leavening, flour, liquid, sugar, oven temperature and baking time and you should have a delicious, made-by-you cake to share.Here's the recipe:
1/4 tsp kosher salt
Read the blog post on Yummly for recipe instructions.