Preheat the oven to 350β/180β. For easy removal of the cake, place parchment paper on the bottom and 2 sides of the pan. Gently grease the two sides without parchment paper and then set aside. Cut the apples, about 2 cups total.
In a medium sized bowl, add in flour, cornstarch, cinnamon, baking powder, baking soda, and salt. Stir to combine and set aside.
2 cups all-purpose flour, 1 tbsp cornstarch, 2 tsp baking powder, 1/4 tsp baking soda, 1 tsp salt, 1/4 tsp cinnamon
In a large bowl, add softened butter and white sugar. Beat on medium speed for 2-3 minutes until itβs light and fluffy. Make sure to scrap the sides of the bowl.
1/2 cup butter, 1 cup white sugar
Add in the egg, egg yolk, vanilla, and yogurt. Continue mixing on medium speed until smooth.
1 egg, 1 egg yolk, 1 tbsp vanilla, 2/3 cups yogurt
Mix in the dry ingredients and using a spatula, gently fold until a batter forms. Do not overmix!
Slice the apples into small cubes and add into the bowl. Gently mix until JUST combined, don't over-mix!
2 cups apples
Spread the batter into the prepared pan evenly. In a small cup, add white sugar and cinnamon and mix together. Then sprinkle on top evenly. This will give you a sweet crunchy top.
2 tbsp white sugar, 1/4 tsp cinnamon
Bake for 35-45 minutes, depending on your oven. It took me 45 minutes. Allow it to cool, slice, and enjoy!
This cake is best eaten day of or next day. Store it in the fridge for up to 5 days in an airtight container.