In a large saucepan, melt the butter over medium heat. When the butter melts, add the pecans and cook, stirring constantly. In a small bowl, stir together the sugar, cinnamon, cayenne, and salt. Just as the pecans start to turn golden brown and fragrant (about 5 minutes), add the sugar mixture to the pan and stir vigorously to coat the pecans. Cook, stirring frequently, until the sugar starts to sizzle and caramelize on the pecans, about 2 minutes more. (Remove the pecans immediately if they show any signs of starting to burn.) Pour the pecans out onto a piece of parchment paper or baking sheet and allow to cool. When cool, break apart and store in a sealed container for up to a week.