Adjust oven rack so cake pan has room to sit center of oven. Preheat oven to 350 degrees Fahrenheit. Grease baking pan then lightly dust with cake flour, set aside.
In a small bowl, sift the baking powder, baking soda, cake flour, and salt together. Set aside.
In a small bowl whisk together all the filling ingredients then set bowl with filling aside.
Whisk butter and sugar which will become a creamy consistency.
Add one egg at a time, beating well after each addition.
Add the coffee concentrate and sour cream then continue to whisk until smooth. (It will look grainy).
Then using a spatula fold sifted dry ingredient into wet batter. Continue until dry and wet ingredients are fully incorporated.
Pour half of the cake batter into the prepared greased pan. Pour coffee filling onto cake batter.
Pour the remaining cake batter on top and gently spread cake batter out with a spatula or spoon.
Bake at 350 degrees Fahrenheit for 35 minutes. To test doneness insert a toothpick, it should come out with moist cake crumbs.
Allow cake to cool in pan for 15 minutes. Remove cake from pan by carefully running a thin cake spatula between the cake exterior and pan. Push out the inner removable tube from bottom. If necessary carefully running a thin cake spatula between the cake and pan. Remove cake then flip to make baked side down be presented as the top.
Dust lightly with powdered sugar. Serve and enjoy with your choice of a hot beverage.