Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan with cooking spray or butter.
In a medium bowl, combine the melted butter, brown sugar, and bourbon. Stir until well mixed. Pour this mixture into the bottom of the prepared cake pan.
Arrange the sliced peaches evenly over the brown sugar mixture in the pan.
In a large mixing bowl, whisk together the flour, granulated sugar, salt, and baking powder.
In another bowl, combine the milk, vegetable oil, eggs, and vanilla extract. Mix well.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix.
Carefully 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.
Remove the cake from the oven and let it cool in the pan for 10 minutes. Then, carefully invert the cake onto a serving plate.
Allow the cake to cool slightly before slicing and serving.