Stir together the sugar, cinnamon, cream of tartar, and boiling water in a small saucepan. Cook over medium heat, stirring constantly, until mixture comes to a boil. Continue to boil until mixture reaches 240° F (soft ball stage) on a candy thermometer, about 8 minutes total.
Remove saucepan from heat, and stir in pecans. Let cool a few minutes, and add vanilla, stirring until pecans are evenly coated. Pour pecans onto a sheet of waxed paper, parchment paper, or a silpat. Separate the nuts with 2 forks. Let cool. Store in an airtight container at room temperature for up to 2 weeks.
Video
Notes
Makes 3 ½ cupsI figured about 1/4 cup serving size