Heat oven to 180C/fan 160C/gas 4. Mix together the butter, sugar and cayenne, then toss through the pecans, and season with salt if you like. Line a baking sheet with parchment paper, then spread out the nuts in a single layer. Cook in the oven for 5 mins. Give the nuts a good stir and cook for another 5 mins or until they are crisp. Remove and leave to cool. You can store the nuts in an airtight container for up to 3 days.