Preheat the oven to 375 degrees F. Butter a shallow 1-quart baking dish. Alternatively, use a 9-inch pie plate or 9-inch square baking pan.
In a large bowl, toss together the strawberries, rhubarb, sugar, salt, lemon zest, lemon juice, and cornstarch. Once well combined, transfer to prepared baking dish.
To make the topping, whisk together the flour, sugar, baking powder, and salt. Use a pastry blender or two forks to cut cold butter into dry ingredients until mixture resembles coarse sand.
Pour in the heavy cream and fold to combine until thick batter forms. Use an ice cream scoop, cookie scoop, or large spoons to portion out mounds of batter over fruit filling.
Lightly brush the batter with heavy cream. Sprinkle turbinado sugar on top.
Bake for 40 to 45 minutes until fruit filling mixture is bubbling and biscuits are golden brown. Allow to cool for a few minutes before serving. Serve with ice cream or whipped cream.