Preheat the oven to 225 degrees F. Line two baking sheets with parchment paper or silicone baking pads (Silpat). In a standing mixer fitted with a whisk attachment, start whipping the egg whites on low speed until the eggs start to foam and then increase the speed to high. Add the cream of tarter. As the eggs start to turn white and come together add the cup of granulated sugar, 1 tablespoon at a time. Continue to beat the eggs until they become stiff and shiny. You are looking for stiff peaks. You can remove the whisk attachment and hold it up to test the peaks.