Preheat the oven to 350 degrees F.
Wash all of the berries and chop the strawberries into into 1/2 inch chunks.
Add the berries to a 9x13 baking dish.
Sprinkle with sugar, cornstarch, and salt. Add in the lemon zest and juice. Stir to combine. Set aside while preparing the topping.
In a medium size mixing bowl stir together the flour, sugar, salt and baking powder.
Cut up the butter into small cubes and using a pastry cutter or a food processor cut the butter into the dry ingredients until coarse meal texture.
Pour in the buttermilk and vanilla extract. Stir to combine.
Using a spoon scoop up the batter and place on top of the berries. Don’t spread it around, it should have a “cobbled” appearance.
Bake for 45-50 minutes until the topping is golden brown and cooked through.
Remove from the oven and let cool briefly before serving.
Top with vanilla ice cream or whipped cream.