Make the caramel: Preheat oven to 350°. In a 10-inch cast iron skillet, melt the butter, brown sugar, and bourbon, stirring to combine, over medium heat. Bring to a boil and boil for 1 minute. Turn off heat.
Carefully, arrange peach slices with one of the cut sides down, in the hot caramel.
In a medium bowl, whisk together flour, sugar, baking powder, and salt. In a large bowl, whisk milk, oil, and egg until well combined. Stir dry mixture into wet mixture until just combined. Pour batter over peaches, spreading to cover evenly.
Bake until top is browned and a tester inserted into the center of the cake comes out clean, 30 to 35 minutes. Let cake cool in pan, 5 minutes, then carefully invert onto a platter. Serve warm or at room temperature.
Recipe by 5* trending recipes with videos at https://food.theffeed.com/2019/07/05/peach-upside-cake/