Preheat oven to 350°F. Over low heat, melt butter in a 10-inch cast iron or other oven-proof skillet. Remove from heat and add brown sugar, stirring to remove lumps and evenly distribute over the bottom of the skillet. Arrange pineapple slices on the brown sugar, six in a circle and one in the middle. Put a cherry in the center of each pineapple ring. Combine pastry flour, white flour, sugar, baking powder and salt in a medium bowl. In a separate bowl, beat the egg. Whisk in the oil, milk and pineapple juice. Add the egg mixture to the flour and stir well to combine completely. Spoon batter over pineapple in the skillet, spreading evenly to the edges of the pan. Bake the cake for 30 to 40 minutes or until a toothpick inserted in the center of the cake comes out free of crumbs. Let the cake cool for 5 minutes before carefully inverting it onto a large round serving platter.