How to Make It
Line a baking sheet with foil; coat foil with cooking spray.
Combine sugar, water, and cream of tartar in a medium saucepan; stir to dissolve sugar. Bring to a boil over medium-high heat. Cook until mixture is golden brown (about 6 minutes), stirring occasionally. Remove from heat, and stir in hazelnuts and vanilla. Spread mixture onto prepared baking sheet. Cool completely. Break into pieces.