Preheat the oven to 350 degrees.
Place 2 tbsp of cut-up butter into a baking dish and transfer into the oven.Heat until the butter is melted.
Meanwhile mix the lemon zest with 1/4 cup of sugar in a bowl.Keep aside.
Combine flour, remaining sugar, baking powder and salt in a bowl.
Whisk in the milk,olive oil into the flour mixture until smooth.
Take the baking dish out of the oven and make sure to spread the melted butter evenly so that it coats the entire bottom of the dish.
Transfer the batter into the dish.Arrange the blackberries evenly over the top.
Sprinkle the lemon sugar and bake until the golden brown edges are crisp about 40-45 mins.Serve warm.