In a medium saucepan, combine diced apples, cinnamon, sugar, and lemon juice. Cook over medium-low heat for about 10 minutes, stirring often. Set the filling aside while you prepare the dough.
On a lightly floured surface, roll out the pierogi dough until it’s about ⅛ inch (3 mm) thick. Use a round cutter (about 7.5 cm (3 inches) in diameter) to cut circles out of the dough.
Place a spoonful of the apple filling in the center of each dough circle. Be careful not to overfill, as it will make sealing difficult. Fold the dough over the filling to create a half-moon shape. Press the edges firmly together to seal, and crimp with a fork to secure.
Place the apple pierogi on a wooden board with parchment paper.
In a large pot, bring water with 1 teaspoon salt to a boil. Carefully drop the pierogi into the boiling water, a few at a time. Cook until they float to the surface, then allow them to cook for another 3-4 minutes.
Remove with a slotted spoon and serve.
Notes
Pick the Right Apples: I like using firm, tart apples like Granny Smith, Honeycrisp, or Braeburn; they hold their shape well and bring just the right amount of tang to balance the sweetness.Taste as You Go: When cooking the apple filling, I always taste it once it softens. Some apples are sweeter than others, so I adjust the sugar as needed. Let it cool completely before filling the dough; this helps keep everything easy to handle.Keep the Dough Soft: I like to keep the dough covered with cling film or a damp cloth while I work, so it stays soft and doesn’t dry out. Rolling it to about ⅛ inch gives the best texture when cooked.Easy on the Filling: I’ve found that about a teaspoon of filling per pierogi is just right; any more and they might burst. I press the edges with a fork for a neat seal and that classic look.Boil Gently: I always make sure the water’s boiling before adding the pierogi, and I don’t overcrowd the pot. When they float, I let them cook for another 3–4 minutes until perfectly tender.Freeze Like a Pro: If I’m making them ahead, I freeze the uncooked pierogi on a tray first so they don’t stick, then pop them into a bag. When I’m ready to cook, I boil them straight from the freezer with just a couple of extra minutes added.