Pour 2 liters of Dr. Pepper into a large heavy sauce pot. Heat to boiling then reduce the temperature to maintain a low boil. Watching closely. Continue cooking until the Dr. Pepper is a thick syrup, and reduced to less than a cup.

Place the prepared apple slices in a large saucepan. Add the apple cider, sugar and 2 teaspoon cinnamon. Place on stove over medium heat. Bring to a boil then reduce heat. Cook for five minutes or until apples just begin to soften. Remove from heat and allow to cool. When cool, remove about ⅔ of the apple slices to place on top of the cake. Choose the prettiest ones! Add the remaining apples and juice to a food processor and pulse to purée. Set aside.

Preheat oven to 350 degrees. Line a 12" springform pan with parchment on the bottom and baking spray the sides.

Whisk the flour, baking powder, baking powder, salt and cinnamon together in a medium bowl and set aside. In a large mixing bowl combine butter and brown sugar and beat until fluffy. Add the eggs, one at a time, beating well after each. Add the Slowly add the dry ingredients in small batches, mixing well after each addition. Fold the yogurt into the batter. Fold in the apple purée until the batter is light and fluffy. You may not need to use all of it if your apples were large. Don't add so much that the batter becomes runny/ I added about a cup of purée to my batter.

Pour half of the batter into the prepared springform pan. Sprinkle the chopped nut on the batter avoiding the edges. Drizzle a couple of TBS of the Dr. Pepper syrup over the nuts. Spread the remaining batter on top of the first layer and spread evenly. Arrange the apple slices in a circle around the cake, completely covering the top. Works best f you start from the middle and work your way out.

Bake on the middle rack in the oven until a toothpick inserted in the center comes out clean. I baked mine for a bout an about but that was a few minutes too long. 45-50 minutes should be fine. Use the toothpick as the guide.

As soon as the cake comes out of the oven, slowly pour half the syrup over the top, allowing it be absorbed into the cake as you go.

Serve with extra sauce, whipped cream, or ice cream as you please. Excellent for breakfast or brunch with a hot cup of coffee.