Prepare the batter: beat the egg, then whisk the milk and salt in a medium bowl.
Stir in the flour a little at a time; mix well until evenly combined;
Add a spoonful of flour in case the batter gets too wet; it should be runny but not watery;
Set the batter aside;
Peel the apples with a potato peeler; then cut the flesh from the core and cut them into rough rings or dice them into pieces;
Squeeze the lemon on the apple slices; toss well so they don’t turn black;
It is time to fry: fill a sauce pan with oil, about an inch (2.5 cm) deep. Heat it over medium heat until it reaches 350°F (175°C): check the temperature with an instant read thermometer. If using a toothpick, put it into the oil, and if bubbles appear, the oil has reached the right temperature.
Dip the apple slices into the batter and coat them evenly. Fry a few slices at a time, 2 or 3, so as to not to lower the temperature. Use a slotted spoon and flip them over until golden;
Transfer them to a paper-towel-lined platter to remove the excess of oil;
In a small bowl, mix powdered sugar with cinnamon;
Sprinkle the fritters with cinnamon sugar. Enjoy them warm; they won’t last long.