01 - Line a large baking sheet with parchment paper and lightly grease. Insert a wooden stick into the stem end of each apple, pushing halfway through.
02 - In a medium heavy-bottomed saucepan, add sugar, water, corn syrup, and cream of tartar if using. Stir gently to combine.
03 - Place saucepan over medium heat and cook without stirring until mixture reaches 300°F on a candy thermometer. Swirl pan gently to prevent hot spots.
04 - Remove from heat; quickly stir in vanilla extract and black gel food coloring until thoroughly blended and even in color.
05 - Tilt pan and carefully dip each apple in hot syrup, swirling to coat evenly. Allow excess candy to drip off, then place on the prepared baking sheet.
06 - Leave apples to cool at room temperature until candy shell hardens, approximately 15 to 20 minutes.