Start by washing and peeling the apples. Then, cut them in quarters and remove the cores. Cut each half of the apple across into slices any thickness you prefer. Then dice the apples across into cubes.
Melt the butter in a medium size pan and add the apples, lemon juice, sugar, ground cinnamon and cornstarch. Bring the mixture to a simmer while stirring constantly. Then lower the heat and cook until the apples have softened, about 7-8 minutes. Transfer the apple filling into a bowl, add the chopped nuts and mix together. Set aside to cool down.
In a large mixing bowl combine the eggs, sugar and lemon zest. Using a hand mixer, whisk the mixture until all the ingredients are combined well.
Next, add the vegetable oil, vanilla extract and whisk again.
After that, add the flour, baking powder and salt. Using a spatula start mixing the dough. The dough should turn out soft and it shouldn’t stick to your hands.
Next, slightly flour the work surface, place the dough on top and roll it into a rectangle about a 1/4-inch-thick. Using a dough scraper form straight edges. Roll the dough again, if needed.
Place the filling in the center of the rectangle. Then fold each side on top. Slightly press the seam.
Using a sharp knife, divide the dough into about 1-inch cookies. I recommend cleaning the knife after each slice.
Place each cookie seam side down on a baking sheet, covered with parchment paper. Bake the cookies at 350 F degrees for 20-25 minutes or until they get a beautiful golden-brown top. Let the cookies cool completely, then decorate with powdered sugar.