Preheat the oven to 375° F.Arrange the peaches in a large baking dish. Sprinkle the brown sugar and butter over the peaches. Add the vanilla. Bake for 30 minutes, or until the sauce is bubbling up around the peaches.Meanwhile, make the better. In a bowl, stir together the melted butter, maple syrup (or honey), egg, vanilla, and milk until combined. Add the flour, baking soda, and salt, and mix until just combined. Remove the peaches from the oven and pour over the batter, do not stir. Sprinkle with cinnamon sugar. Bake for 30-40 minutes, until the center is just set and the edges begin to brown.Serve the cake warm or at room temp with ice cream.