Preheat oven to 375°F.

Combine flour, baking powder, sugars, lemon zest, and melted butter in a mixing bowl. Mix until clumps form; set aside.

In a deep 9-inch pie-plate, combine rhubarb, strawberries, lemon juice, sugar, cornstarch, and salt. Mix until incorporated.

Add the prepared topping over the fruit mixture.

Place the pie plate on a foil-lined baking sheet and bake for 45 minutes, or until the topping is golden brown and the fruit is bubbly.

Remove from oven and let stand for 8 to 10 minutes.

Serve.