Prep: Preheat the oven to 300°F and line a baking sheet with parchment paper.
Mix nuts: Stir together the ground hazelnuts and cinnamon in a small bowl.
Whip whites: Beat the egg whites and salt in a clean bowl until soft peaks form.
Add sugar: With the mixer running, add the sugar a spoonful at a time. Beat until thick, glossy, and stiff peaks form.
Add vanilla: Beat in the vanilla just until mixed.
Fold: Gently fold the hazelnut mixture into the meringue until evenly combined.
Scoop: Drop 1½-tablespoon mounds onto the baking sheet, 1½ inches apart. Press a whole hazelnut on top of each.
Bake: Bake 23 to 25 minutes, until the edges are lightly golden and the tops feel dry.
Cool: Cool completely on the baking sheet before removing. If they stick, bake a few minutes longer.