Preheat oven to 350°F. Grease a 9-inch angel food cake pan (or bundt pan).

In a large mixing bowl, beat butter and brown sugar until creamy. Add Greek yogurt, apple butter, vanilla extract, and maple extract, mixing until smooth. Beat in eggs, one at a time.

In a separate bowl, whisk together flour, baking powder, baking soda, apple pie spice, and salt. Gradually add the dry ingredients to the wet mixture, stirring until just combined. Mix in the bourbon.

In a medium bowl, combine flour, brown sugar, and apple pie spice. Add grated cold butter and rub with fingers until crumbles form.

Spoon half the batter into the prepared pan. Sprinkle with chopped apples and half the streusel. Add the remaining batter in an even layer. Arrange thin apple slices on top, then finish with the rest of the streusel.

Bake 60–65 minutes, or until a toothpick inserted in the center comes out clean. Cool for 30 minutes. Invert the cake onto a plate, then flip right-side up onto a serving plate.

In a small saucepan over medium heat, melt butter with maple syrup. Whisk in powdered sugar, bourbon, and salt until smooth. Drizzle over the cake. Let set 10 minutes before serving.

Store covered in the fridge. Enjoy warm or at room temperature.