Preheat your oven to 300°F (150°C). Line a large rimmed baking sheet with parchment paper or a silicone baking mat for even baking and easy cleanup.

In a large mixing bowl, whisk the egg white and water together until very frothy and slightly thick, about 30–60 seconds by hand. Whisk in the vanilla extract.

Add the pecan halves to the bowl with the egg white mixture and toss until every nut looks glossy and evenly coated, with no dry patches.

In a separate bowl, stir together the granulated sugar, light brown sugar, ground cinnamon, fine sea salt, and optional nutmeg or allspice and cayenne. Break up any brown sugar clumps so the mixture is even.

Sprinkle the cinnamon sugar mixture over the wet pecans in 2–3 additions, tossing well after each addition until every pecan is thoroughly coated and only a light dusting of loose sugar remains in the bowl.

Pour the coated pecans onto the prepared baking sheet and spread them into an even, single layer. Some touching is fine, but avoid a thick pile so they roast instead of steam.

Bake at 300°F (150°C) for 35–45 minutes, stirring every 10–15 minutes. Each time you stir, bring the nuts from the edges toward the center and break up any clumps. The coating should look dry and crisp, and the nuts should smell toasty and strongly of cinnamon when they’re done.

Remove the pan from the oven and give the pecans one last gentle stir. Spread them out again in an even layer and let them cool completely on the pan; they will crisp up further as they cool.

Once completely cool, break apart any large clusters with your fingers. Taste and add a tiny sprinkle of extra salt if you like more salty-sweet contrast. Store or serve as desired.