Preheat oven to 350 degrees. Line a large baking sheet with sides with aluminum foil. Pour the butter onto the lined sheet. In large bowl, mix egg whites, sugar, and cinnamon. Add pecan halves and toss until they are fully coated. Spread pecans onto baking sheet. Bake 30 min, stirring pecans every 10 min. Cool on baking sheet for 10-15 min before serving.