Preheat oven to 375 degrees.
Spray a 9”x 6” baking dish with non-stick baking spray.
In a large bowl add the berries.
Drizzle the berries with lemon juice.
Toss to combine.
Add the cornstarch to the berries and toss to combine.
Allow the berries to marinate for 20 minutes.
In a separate large bowl whisk together the flour, baking powder, and salt.
Set to the side.
In the bowl of a stand mixer, beat the butter, brown sugar, and vanilla until well-blended.
Slowly add in the dry ingredients until the mixture resembles little crumbs.
Pour the berries into the baking dish.
Drop the dough evenly on top of the berries.
Bake for 30 minutes, or until the top is lightly browned.
Enjoy