Preheat smoker (or oven) to 350°F.
Prepare the topping. Combine flour, baking powder, baking soda, granulated sugar, and salt in a large mixing bowl. Cut butter into 12-14 slices and press into mixture. Stir in the buttermilk with a wooden spoon and set aside.
Prepare the filling by thoroughly whisking brown sugar, vanilla, maple syrup, flour, cinnamon and lemon juice, then add peaches.
Add filling mixture to a greased, 12” cast iron skillet, then drop dollops of topping over the top. Smoke (or bake) 40-45 minutes, rotating occasionally, until golden brown and bubbly.
Serve warm with a scoop of vanilla ice cream!