Beat egg whites until foamy in a large glass or metal mixing bowl until soft peaks form. Lift your beater or whisk straight up: the egg whites will form soft mounds rather than a sharp peak.
Mix the pecan halves into the egg white.
Stir the white sugar, brown sugar, and cinnamon together in a bowl; add to the pecan and egg white mixture and stir.
Coat the bottom of a jelly roll pan with the softened butter.
Spread the pecan mixture in an even layer in the prepared pan.
Bake in the preheated oven until crisp, turning occasionally, 45 to 60 minutes.
