Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan with cooking spray or butter.

In a medium saucepan over medium heat, melt the butter. Stir in the brown sugar and bourbon until combined. Cook for 1-2 minutes until the mixture is bubbly and slightly thickened. Pour this mixture into the prepared cake pan.

Arrange the sliced peaches evenly over the brown sugar mixture in the pan.

In a large bowl, whisk together the flour, baking powder, baking soda, and salt.

In another bowl, beat together the granulated sugar, applesauce, eggs, and vanilla extract until smooth. Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, starting and ending with the dry ingredients. Mix until just combined.

Pour the batter over the peaches in the cake pan, spreading it evenly.

Bake for 35-40 minutes or until a toothpick inserted into the center comes out clean. Let it cool in the pan for 10 minutes.

Carefully invert the cake onto a serving plate, allowing the peaches to be on top. Serve warm or at room temperature.