Mix 3 cups all-purpose flour with 2 teaspoons baking powder and pour the mixture into a large mixing bowl. Add 1 cup granulated sugar, 1 egg, and 1 Tablespoon lemon zest to the dry ingredients. Incorporate 1 ¾ sticks unsalted butter, cut into smaller slices.
Use your fingers to work everything into irregular clumps. This step might take some time and physical effort, but it is nothing you couldn't handle!
Prepare the apples: Peel 6 large apples using a peeler, then remove the cores with a core remover. Place the peeled apples in a separate bowl. Using the side with large holes on a box grater, shred the apples. Be sure to retain the juice from the grated apples in the bowl!
Add ⅔ cups granulated sugar, ½ teaspoon groung cinnamon, ½ teaspoon vanilla paste, and 2 Tablespoons cornstarch to the shredded apples. Stir until combined.
Line a baking dish with parchment paper. Here's a simple trick to keep the paper from curling or sliding: Crumple it into a ball, dip it in water, squeeze out the excess, and then spread it out again. Place the damp parchment paper on the bottom of the baking pan.
Make the apple cake with three layers. First, divide the crumb mixture into two equal halves. Spread one half of the crumbs on the bottom of the lined baking pan. Next, add a layer of shredded apples, smoothing the surface evenly. Finally, sprinkle the remaining half of the crumb mixture over the apples.
Preheat the oven to
340 °F using both lower and upper heat settings. Place the pan with the apple cake in the oven and bake for 40 minutes, or until the surface turns golden brown.