Preheat the oven to 330 degrees F (165 degrees C).
In a large glass or metal bowl, whip egg whites with cream of tartar and salt until soft peaks form. Gradually sprinkle in the sugar while continuing to whip to medium peaks. Since this is a high-altitude recipe, whip them only until they form a peak that falls over. Stir in the vanilla and lemon extracts. Use a rubber spatula to fold in flour a fourth at a time. Spoon into a clean and dry 9 inch tube pan.
Bake for 25 minutes in the preheated oven, then increase the temperature to 375 degrees F (190 degrees C). Continue baking for another 3 minutes, or until the cake begins to shrink down a bit. Invert pan over a wire rack to cool. When cool, run a thin spatula or knife around the outer edge, and tap out firmly.
