Preheat the oven to 350°. Place an 8-9 inch cake pan on a sheet of parchment paper and trace around the bottom. Cut out the circle. We used a 9-inch round cake pan. Spray the cake pan with olive oil and then place the cut out parchment in the bottom and spray the paper.
Thinly slice the peaches, leaving the skin on. Place flat in, circles, starting in the center, and moving out toward the edge.
Melt the ¼ cup butter in a saucepan on medium heat. Add in the brown sugar and whisk over the heat for about 1 minute. Stir in the cinnamon if you desire to.
In a stand mixer bowl or a mixing bowl with electric beaters, place the ½ cup of softened butter and ¾ cup white sugar. Cream together. Add in the eggs, one at a time, mixing between each egg. This method will improve the crumb texture of the cake. Add in the vanilla extract and mix it in.
Measure the flour and baking powder into a small mixing bowl. Use a whisk to smooth it out or sift it.
Measure out the milk. Add half of the dry ingredients and then mix in thoroughly. Next add in the milk and mix it in. Now add in the rest of the flour mixture and fully mixt it in.
Carefully pour the batter over the peaches into the cake pan, scraping the bowl with a rubber spatula. Smooth over the top.
Bake at 350° for 35-40 minutes. Take out and cool for 15 minutes before flipping it onto a plate or platter.
Place a plate over the cake and grab tight with hot pads or oven mitts, then flip over and remove the cake pan carefully. Now gently pull off the parchment paper if it comes over off with the peaches. Cut into slices and serve on its own or with whipped cream or ice cream.