Preheat oven to 350°F and spray a 9-inch cake pan with baking spray.
In a large bowl, add melted butter, sugar, vanilla, and milk. Mix on medium speed with an electric mixer until incorporated.
Add eggs one at a time, beating after each. Mix in flour and fold in pecans.
Arrange half of your peaches in the cake pan and pour batter over the top, smoothing with a spoon. Arrange second half of peaches over the top. (I had about 22 peach slices total.)
Bake for 1 hour, tenting with foil halfway through baking to prevent too much browning around the edges.
Let cake cool; best served warm with powdered sugar on top and a scoop of ice cream.