• Preheat your oven to 180°C / 350°F

Make the Crust

• In a medium bowl, combine the melted (and cooled) butter with the sour cream. Add the flour, baking powder, and a pinch of salt. Gently knead until a soft, smooth dough forms.
  
• Press the dough evenly into the bottom and up the sides of a greased or parchment-lined baking pan (a tart pan or springform pan works best).
  
• ...create a neat border.
  
• Prick the entire surface of the dough with a fork.
  
• Peel the apples,
  
• Core them, and chop into small pieces. Arrange them evenly over the crust.
  
• If your apples are on the sweeter side, drizzle them with fresh lemon juice to balance the flavor.
  

Make the Filling

• In a mixing bowl, beat the egg and sugar together with a mixer until slightly fluffy.
  
• Add the sour cream and vanilla, mixing well to combine.
  
• Stir in the flour and give it one final mix.
  
• Pour the sour cream filling evenly over the apples.
  
• Optional: At this point, you can scatter some berries over the top - blackcurrants add a lovely tart pop of color and flavor, though it's completely optional!
  
• Bake for 45 to 55 minutes until the top is a beautiful golden brown. (Baking time may vary depending on your oven and the type of pan used). To test for doneness, insert a knife blade or a wooden skewer into the center of the pie - it should come out clean.
  
• Dust lightly with powdered sugar before serving. Enjoy!