Make the Cake Batter

1. Preheat the oven to 350°F and grease the cake pan.
2. In a medium bowl, create the flour mixture. Combine flour, baking powder, baking soda, and salt; set aside.
3. In a large mixing bowl, beat the six tablespoons of the softened Butter and sugar until light. Add yogurt, eggs, and vanilla, and blend well.
4. Alternately add the dry ingredients and butter mixture.
5. Beat well but gently after each addition. This ensures a tender cake.
6. Spread the batter in the prepared pan.

Make the Cinnamon Streusel Topping

1. In a small bowl, combine streusel ingredients well except Butter. 
2. Cut in 2 tablespoons of cold Butter until crumbly using a pastry cutter or a large fork.
3. Ensure all ingredients are mixed well, and you have a well-integrated streusel.

Instructions for the Apples and Dulce de Leche Cake Toppings

1. Sprinkle half of the streusel topping over the batter.
2. Thinly slice the unpeeled apples into approximately 1/8 thick slices. 
3. Arrange apple slices over the batter, staggering them in a circular shape starting from the outside and making your way to the middle of the cake.
4. Sprinkle the remaining streusel topping over the apples.
5. Bake at 350°F for 30-35 minutes or until a toothpick inserted in the center of the cake comes out clean. Cool for 10 minutes on a wire rack
6. In a microwave-safe bowl, combine dulce de leche and water and microwave for 20-30 seconds.
7. Drizzle over the apple cake. Enjoy!