In a medium bowl, combine flour, baking powder, sugar, salt, and 1/4 teaspoon cinnamon. Set aside.

In a small bowl, whisk together the buttermilk and beaten egg.

In a third bowl, mix 1/3 cup sugar and 2 teaspoons cinnamon. Set aside for topping.

Slice apples into 1/4-inch rings. Use a biscuit cutter to core them, creating ring shapes. Pat dry with paper towels.

Heat vegetable oil in a frying pan over medium-high heat to 350°F (175°C).

Mix the dry ingredients with the wet buttermilk mixture to create a smooth batter.

Dip each apple ring into the batter, letting excess drip off.

Fry in batches, turning as needed, until golden and crispy on both sides.

Transfer fried rings to a paper towel-lined plate to drain.

While still warm, coat in cinnamon sugar and place on a wire rack to prevent sogginess.

Serve warm and enjoy!