Preheat oven to 350 F.
Place a 10-inch cast iron skillet in oven while it preheats.
Whisk together flour, sugar, baking powder, and salt in a medium bowl.
Whisk together the milk, vanilla bean paste, lemon zest, and lemon juice in another bowl.
Add milk mixture to flour mixture, stirring just until combined.
Place butter in cast iron skillet in oven and bake until butter melts.
Add batter to hot skillet.
Scatter blueberries and peaches over the top.
Sprinkle turbinado sugar over the top.
Bake for 50 minutes or until golden brown. Serve warm or at room temperature with ice cream.