Begin by preheating your oven to 350°F (175°C). Line a baking sheet with parchment paper to facilitate easy cleanup later.
In a generous mixing bowl, combine the brown sugar, ground cinnamon, sea salt, and optional cayenne pepper. Stir the mixture well to ensure even distribution of the spices.
In a separate small bowl, whisk together the melted butter and pure vanilla extract until fully combined and slightly frothy.
Pour the butter and vanilla mixture over the pecan halves in the large mixing bowl. Use a spatula or your hands to toss the pecans, ensuring that each one is thoroughly coated with the buttery goodness.
Sprinkle the combined sugar and spice mixture over the butter-coated pecans. Stir gently yet thoroughly until all the pecans are evenly coated in the sweet and spicy mixture.
Transfer the coated pecans onto the lined baking sheet. Spread them out in a single layer to ensure even roasting.
Bake the pecans in the preheated oven for 15-20 minutes. Be sure to stir them halfway through the baking time to promote even browning. Keep a vigilant eye on them, as they can quickly go from golden to burnt.
Once they are golden brown and exude a delightful aroma, remove the pecans from the oven. Allow them to cool on the baking sheet; they will harden as they cool, becoming perfectly crunchy.
When they have completely cooled, break apart any clusters that have formed and transfer the pecans to an airtight container for storage.
Notes
Keep an eye on the pecans while baking to prevent burning.