Preheat oven to 350°F. Line rimmed baking sheet with foil. Spray foil with nonstick spray. Whisk egg white in medium bowl until foamy. Add sugar; whisk until frothy. Whisk in rosemary, fleur de sel, and cayenne. Add nuts; stir. Transfer to baking sheet, spreading nuts in single layer. Bake until golden, stirring every 10 minutes, about 40 minutes. Cool completely on sheet. (Can be made 1 day ahead. Cover; store at room temperature.) *A type of sea salt, available at specialty foods stores and some supermarkets.