Preheat the oven to 400°F and set it to convection mode. Line a baking sheet with parchment paper.
Wash the berries, pat them dry, and dust with two tablespoons of flour. Set aside ⅔ cup of berries for topping the cake later.
In a bowl, mix the remaining flour, eggs, buttermilk, vanilla extract, and one cup of sugar until a smooth batter forms. Make sure to add the baking powder last.
Pour the batter evenly onto the baking sheet, then scatter the majority of the berries on top. Evenly coat the remaining sugar over everything.
Bake the cake for 20 minutes. Shortly before the end of the baking time, do a toothpick test. If it doesn't come out clean, continue baking for another 5 minutes.
Once baked, let the cake cool. Then top with the reserved berries and sprinkle with powdered sugar.