Preheat your oven to 300F and line a large baking sheet with parchment paper.
In a medium bowl, whisk the egg white, vanilla extract, and cream of tartar until frothy and slightly foamy, about 1 minute.
Add the almonds to the egg white mixture and toss until every almond is evenly coated.
In a small bowl, stir together the erythritol, cinnamon, and salt. Sprinkle this mixture over the coated almonds and toss thoroughly until every nut is covered with the cinnamon sugar blend.
Spread the almonds in a single layer on the prepared baking sheet, making sure none are stacked on top of each other.
Bake for 30 to 35 minutes, stirring every 10 minutes, until the coating is dry and the almonds smell toasty and fragrant.
Let cool completely on the baking sheet. The coating will harden and become crunchy as the almonds cool. Store in an airtight container for up to 2 weeks.