Mix the berries with 1/4 cup (50g) sugar. Spread evenly in a 9"x 13" baking pan.
Whisk together the flour, baking powder, and salt. Set aside.
In a separate bowl, whisk the eggs, olive oil, lemon zest, vanilla, and 1 cup sugar. Stir in the flour mixture until just combined. Pour evenly over the berries.
Bake 30 to 35 minutes, or until the top springs back slightly in the center.
Cool at least 10 minutes before serving.
Sprinkle with confectioners' sugar or add a dollop of sweetened whipped cream just before serving.