Fill a medium-sized bowl half-full of cold water and add the juice of ½ of a lemon. Slice the apples horizontally into ¼" to ⅜" rounds. (The thicker the slice, the more firm the apple will be after it is cooked.) You may choose to peel the apples before slicing if you want to remove the skin, but it is not necessary. Use a small round cookie cutter or paring knife to remove the core out of each slice and immediately submerge the apples in the lemon water. Repeat until all of the apples have been sliced.
In a separate medium-sized bowl, whisk together the flour, baking powder and salt. Pour in the beaten egg and apple cider and stir just until combined. It is okay if a few lumps remain. Set the batter aside and stir together the sugar and cinnamon in a separate small bowl. NOTE: We strongly recommend you weigh your einkorn flour, if possible, for better accuracy. If you don’t have a scale, fluff the flour with a fork before you measure it in a cup.
Place a large pot over medium heat and add 1½"–2" of oil. Place a cooking thermometer into the oil and heat to 350 degrees. At this point, you will also want to line a tray or baking sheet with paper towels to drain the slices after they are removed from the oil.
Once the oil has reached the correct temperature, remove several slices of apple from the water and blot completely dry with paper towels. Dip each slice into the batter and tap lightly on the side of the bowl to remove any excess. Carefully slide the apple slice into the oil and repeat with as many slices as will fit in a single layer. (Do not overcrowd the oil or the temperature will drop, leaving you with greasy apple slices.)
Fry the slices for about 1½ minutes on each side before removing them to drain on the paper towel-lined tray. Repeat with all remaining ingredients. While the slices are still warm, coat each of them in cinnamon sugar. Serve warm and enjoy!
Make sure you never walk away from a pot full of hot oil! It helps to have everything prepped and ready before you start the frying process.