Preheat oven to 350 degrees F. Butter and flour an 8 x 8-inch brownie pan.
Cream butter, sugar, and 1/2 tsp ground cinnamon using an electric mixer.
Beat your eggs one at a time, followed by vanilla extract. Stir in sifted flour until completely mixed through moistly.
Fold in apple pieces gently with a spatula, one spoonful at a time until the mixture is smooth.
Bake for 30 minutes or until golden on topsides are firm to the touch and moist inside.
Allow cake to cool in pan before turning out onto wire rack, then flip right side up and remove the attached paper bin order to glaze it before it completely cools.
Once the cake cools down, slice it up and enjoy!