Preheat the oven to 325°F and line a sheet pan with parchment paper.
Melt the butter using the microwave or stovetop. Add the brown sugar, cayenne, salt, rosemary, and pecans to the butter and stir well to coat the pecans evenly.
Spread the pecans out evenly on the sheet pan, making sure to get all of the coating out of the bowl and onto the pan. Bake for 15 minutes.
Remove the pan from the oven. Stir the pecans well, moving ones from the edges to the center. Bake for an additional 10-15 minutes, or until deeply toasted (but not burned!).
Remove the pan from the oven and stir the pecans again. Allow them to cool in the pan completely, stirring occasionally. They will continue to absorb the butter.
Once cool, stir the pecans and breakup any clusters and store them in an airtight container at room temperature.
Nutrition facts are sometimes provided below and are calculated using an online calculator. With specific brands of ingredients and additions, omissions, or substitutions the nutrition facts may change. We encourage you to use your own nutrition facts calculator to obtain the most accurate nutrition facts for your meal.