In a large bowl, whisk together the flour, 1/4 cup granulated sugar, baking powder, salt, and 1/2 teaspoon cinnamon.

In a separate medium bowl, whisk together the egg, milk, and vanilla extract until well combined.

Gently fold the wet ingredients into the dry ingredients until just combined. Do not overmix; a few lumps are okay.

Fold in the diced peaches.

In a large, heavy-bottomed pot or Dutch oven, heat the vegetable oil over medium-high heat until it reaches 350°F (175°C) on a candy thermometer. If you don't have a thermometer, a wooden spoon dipped into the oil should bubble vigorously.

Carefully drop heaping tablespoons of the batter into the hot oil, being careful not to overcrowd the pot. Fry in batches for about 3-4 minutes per side, until golden brown and cooked through. Use a slotted spoon to turn the fritters.

Remove the fritters from the oil and place them on a wire rack set over paper towels to drain any excess oil.

While the fritters are still warm, combine the remaining 1/4 cup granulated sugar and 1/2 teaspoon cinnamon in a shallow dish. Toss the warm fritters in the cinnamon sugar mixture until evenly coated.

Serve warm, either on their own or with a dusting of powdered sugar or a drizzle of maple syrup.