Add oil to a large deep pot. Fill it about 2-inches full or enough to cover the fritters by about 3/4. Heat over a medium-high flame until it reaches 375 degrees.
Line a baking sheet with paper towels.
While the oil heats, make the batter. Add flour, baking powder and salt to a medium bowl. Set aside.
Add egg and sugar to a large bowl. Use a wooden spoon or whisk to beat the egg into the sugar for 2 minutes. Add in the melted butter, orange juice and vanilla. Beat again until combined.
Pour in half of the milk. Stir until combined. Gently add in half of the flour mixture. Stir until combined. Add in the apples, gently fold in. Add in remaining milk, gently stir until combined. Add last half of flour, gently stir until combined.
Test the oil. Place a wooden in the oil, handle side down. If the oil bubbles vigorously around the wooden spoon, the oil should be ready to go.
Once the oil is hot, measure out one tablespoon of the batter. Use your finger to GENTLY push the batter off the spoon and into the batter. Use a slotted spoon to make sure the fritter doesn't stick to the bottom of the pan after it drops in the oil. Add more fritters to the oil but be sure you don't crowd the pan. I used a 10-inch pot and got about 5-6 fritters per batch.
Let the fritters fry until golden brown, about 2-3 minutes. Flip and repeat on the other side. You want them golden brown on all sides. Use a slotted spoon to scoop the fritters out of the oil. Drain on paper towels. Sprinkle with powdered sugar while hot.