Preheat oven to 350 degrees F (176 C) and add hazelnuts to a baking sheet in a single layer. Roast for a total of 12-15 minutes, or until fragrant and golden brown.
Remove from oven and let cool slightly. Then transfer to a large kitchen towel and use your hands to roll the nuts around and remove most of the skins (see photo). You want to get as much as possible off because it yields a creamier nut butter. But it doesn’t have to be perfect!
Leaving excess skin behind, scoop hazelnuts into a food processor or high speed blender. Blend on low until a butter begins to form – about 7-9 minutes total – scraping down sides as needed.
Once the hazelnut butter is creamy and smooth, add the ground cinnamon, sea salt, and coconut sugar (optional).
Blend/puree again until well incorporated. Taste and adjust seasonings as needed.
Transfer hazelnut butter to a clean jar and store at room temperature for up to 1 week, or in the refrigerator for up to 2 weeks (or more).