First, take 2 tbsp Ground Flax + 6 tbsp WATER and allow to sit for 5 minutes or unless using applesauce.
Preheat oven to 350 degrees. Use an 8x8 or 9x5 pan and spray with non-stick spray or line with foil or parchment paper and spray with non-stick spray to get out easily for slicing.
Mix 1/3 cup brown sugar and 1 teaspoon cinnamon together in a bowl. Set aside.
Combine & whisk 1 & 1/2 cups flour and 1 & 3/4 teaspoons baking powder together in another bowl and set aside.
In another medium-sized bowl, beat 2/3 cup granulated sugar and 1/2 cup softened butter together using an electric mixer until smooth and creamy.
Beat in 2 flax eggs or applesauce until blended in; add in 1 & 1/2 teaspoons vanilla extract and mix in.
Add the flour mixture into creamed butter mixture and mix until blended.
Mix 1/2 cup milk into batter and continue mixing until smooth.
Pour half the batter into the prepared pan; add half the chopped apple mixture with the sugar and cinnamon added in.
Sprinkle 1/2 of the brown sugar/cinnamon mixture you set aside earlier, on top of apple layer.
Pour the remaining batter over apple layer and top with remaining chopped apples, then the remaining brown sugar/cinnamon mixture.
Lightly pat apples into batter; swirl brown sugar mixture through apples using knife or spoon.
Bake in the preheated oven until a toothpick inserted in the center of the cake comes out clean, approximately 45-50 minutes for 8x8 pan and 60 minutes for a 9x5 pan.