Mix dry ingredients and wet ingredients in separate bowls: In a large bowl, whisk together flour, granulated sugar, baking powder, and salt. In another bowl, whisk together milk, eggs, butter, and vanilla.
Fold wet ingredients into dry; mix in apples: Gently fold milk mixture into flour mixture until just combined. Fold in apples.
Heat oil in heavy pot; set wire rack over baking sheet: NO IMAGE Meanwhile, heat 2 inches of oil in a medium heavy-bottomed pot over medium-high heat until a thermometer registers 350°F. Set a wire rack in a rimmed baking sheet.
Cook fritters in batches; cool on rack and dust: Working in batches, drop heaping tablespoons of dough into oil. Cook, turning once, until puffed and golden, 3 to 4 minutes. Transfer to rack with a slotted spoon. Let cool slightly, dust with confectioners' sugar, and serve.
