Melt the butter in a small bowl and combine with the maple syrup, cayenne pepper, and 1 tablespoon of the chopped rosemary.
Pour the mixture over the nuts and toss to coat them evenly.
Bake for about 10 minutes, then toss once more.
Bake for 5-10 minutes longer, or until the nuts are golden brown and fragrant.
Remove from heat and immediately toss with the additional ½ teaspoon rosemary and flaky sea salt, to taste.
