Preheat oven to 375°F (190°C).
In a large bowl, combine strawberries, rhubarb, sugar, cornstarch, lemon juice, and salt. Let sit 10–15 minutes.
Pour the fruit mixture into a greased 9x13" baking dish.
In another bowl, mix flour, sugar, baking powder, and salt.
Cut in the butter until the mixture resembles coarse crumbs.
Stir in milk to form a soft dough.
Drop spoonfuls of topping evenly over the fruit.
Bake for 40–50 minutes, or until the topping is golden and the filling is bubbling in the center.
Let cool for 10 minutes before serving.