Preheat the oven to 350˚F.
Place the butter in a small sauce pan and set on the stove at low heat. Once the butter is fully melted, allow to cool for 5-10 minutes.
While the butter melts, peel and grate the apples using a cheese grater. Set the grated apples into a strainer and squeeze gently to remove excess water. Set the apples aside.
In a medium sized mixing bowl, combine the dry ingredients: flour, baking powder, baking soda, salt, ginger, nutmeg, cardamom, and 1 teaspoon of the cinnamon. Whisk gently to blend them all together.
In a smaller, separate bowl measure out the brown sugar and the other teaspoon of cinnamon and set aside.
In a separate, larger mixing bowl whisk together the sugar and melted (but slightly cooled) butter.
Whisk in the eggs, sour cream and vanilla.
Pour the bowl of dry ingredients into the bowl of wet ingredients all at once. Using a rubber spatula, gently fold in the dry ingredients until fully combined, but take care not to over mix. The batter will be very thick, almost like a dough.
Once there are no dry spots of flour, gently fold in the grated apples until they are evenly distributed throughout the batter.
Finally pour in the brown sugar/cinnamon mixture. Fold in gently and only fold about 5-7 times total. To create distinct "swirls" of brown sugar, you don't want to fully incorporate the brown sugar.
Gently scoop the batter into your loaf pan, spreading it evenly on the top, but handling it as little as possible.
Set in the oven to bake 1 hour and 15 minutes- until a toothpick comes out clean when poked through the center.
Allow to cool at least 20 minutes before removing from the pan and cutting into slices.
Serve with a small scoop of vanilla ice cream, a drizzle of caramel syrup, or enjoy as-is!