Preheat the oven to 350˚F. Grease a 9-inch springform pan
In a large mixing bow, whisk together flour, sugar, baking powder, salt. Add the butter pieces and mix with flour mixture using a dough scraper or fingers until it resembles breadcrumbs.
Add the egg and mix with a fork first, then use your finger to moisten the flour mixture until it becomes crumbs.
Sprinkle half the amount of the crumbs in the pan and gently press down to form a crust.
In another mixing bowl, combine berries, sugar, lemon zest, lemon juice, and cornstarch; mix well. Pour on the crust and spread evenly.
Sprinkle the rest of the crumbs to cover the berries. Bake for 40 minutes or until the top gets light golden brown. Let the cake cool in a pan for 10 minutes. Remove from the pan and cool completely.