Preheat the oven to 350°F (175°C).
In a mixing bowl, combine apples, berries, sugar, and lemon juice. Toss to coat the fruit evenly.
Spread the fruit mixture evenly in the bottom of a baking dish.
For the topping, combine flour, baking powder, and salt in a separate bowl.
Stir in melted butter and milk until the batter is smooth.
Pour the batter evenly over the fruit mixture.
Bake in the preheated oven for 40 minutes or until the top is golden brown and the fruit is bubbly.
Let cool slightly before serving.