In a small saucepan, add the brown sugar, cinnamon, salt, and water. Stir to combine with a silicone spatula.
Place the pan over medium-high heat and cook the sugar mixture until the mixture boils. Do not stir the sugar mixture at this point. Stirring can cause the sugar to crystallize.
Once boiling, add the toasted pecans and very quickly mix to cover them with sugar. Do NOT stir too much. The agitation will cause crystallization.
Cover the saucepan and continue boiling for approximately 1 minute or until the mixture reaches the hard crack stage (i.e., 300F/149C).
Quickly transfer the pecans to a baking sheet lined with parchment paper and use a fork to separate the pecans. This process needs to happen VERY quickly because the sugar mixture will harden within a couple minutes. Be careful during this process because the sugar is very hot and can burn you.
I like to make small batches of candied cinnamon pecans so it’s easier to separate all of the pecans before they harden. If you make a larger batch, keep the pecans in the saucepan so the sugar stays warm while you separate the pecans onto the baking sheet.
Allow the candied pecans to cool until hard and are no longer sticky.