Overbeating adds too much air to the cake. At elevations over 3,500 feet, the oven temperature for batters and doughs should be about 25 degrees F higher than the temperature used at sea level. Foam cakes have a very delicate egg protein structure. Reduce sugar slightly to help compensate for the liquid loss. Increase whole eggs or egg whites to compensate for the liquid loss.
Cakes tend to stick more when they are baked at high altitudes.
So be sure to always grease your baking pans well and dust them with flour or line them with parchment paper. Exceptions are angel food cakes and sponge cakes, which should always be baked in ungreased pans. Follow the chart below for more specific adjustments. When adapting a recipe for high altitudes always start out with the smallest adjustment, then add more adjustments later and only if necessary. Keep in mind that any or all of these adjustments may be required, for every recipe is different in its balance of ingredients.