Preheat the oven to 325 degrees and line a large rimmed baking sheet with parchment paper or a silicone baking mat.
In a small bowl combine maple syrup, melted butter, salt, vanilla, and cayenne if using. Whisk to combine well.
Add the nuts to the prepared baking sheet and pour the maple spice mixture over the nuts and stir well until all of the nuts are lightly coated.
Spread the mixture in a single layer across the pan.
Bake for 20-25 minutes, stirring after the first 10 minutes and then every 5 minutes until almost no maple syrup remains on the baking sheet and the buts are a deep golden color.
Remove the pan from the oven and stir the nuts once more, spreading them to an even layer. They will be a bit sticky right out of the oven. Let them for about 8 minutes and separate any large clumps while the nuts are slightly warm if necessary.
Let the nuts cool completely on the pan and store in a sealed bag or jar at room temperature.