• Preheat oven to 350 degrees. Line a baking sheet with parchment paper.

  In a large bowl, whisk together sugar, egg, sour cream, and vanilla extract until completely combined. Add softened butter.

  In a separate bowl, whisk together flour, baking soda and salt.

  Add dry ingredients to wet and stir to combine. Knead until it just comes together, then mold into two balls.
• Place each of the balls onto a parchment paper. Roll out each ball into large flat ovals using a rolling pin on two separate parchment papers. Place first oval onto a cooking sheet.
• Slice apples thinly and set aside.
  
• Add sliced apples on top of the first oval. Cover the apples with the second oval (you will carry it with the parchment paper) and pinch together to seal. Using a fork, pierce the top layer in multiple places and make a hole in the middle of the top layer.

Crumb Topping

• Add flour, sugar to the bowl. Cut butter into small pieces and use your fingers to rub in the butter. Use just your finger-tips (not your warm hands) and quick motions, pinching your fingers to mash the small pieces of butter into the dry ingredients until moist crumbs form.
  
• Add crumb topping on top.
• Bake for 35 to 45 minutes, or until a toothpick inserted in the center comes out clean.