Heat a large saucepan or skillet pan on medium heat. When hot, add the sugar, water, vanilla extract, salt, and cinnamon, if using it, and mix until fully combined. Allow to heat up, stirring occasionally.
When the sugar has completely dissolved, add the raw, unsalted pecans. Watch over the pan and continue stirring often until most of the sugar mixture has been coated and beginning to crystallize.
Remove pan from the heat and allow to sit for 1-2 minutes, before using a wooden spoon to stir almonds together to avoid immediate, overlarge clusters forming. Allow to cool completely before breaking up properly.
Notes
Oven method: In a large bowl, whisk all the ingredients together before adding in the pecans. Toss to coat, then place them in a single layer on a baking sheet lined with parchment paper and bake at 120/250F for around an hour, stirring the pecans every 15 minutes.