Preheat the oven to 350°F.

Lightly grease a 9x13 baking dish with butter.

Wash the berries and spread them evenly in the baking dish. Sprinkle with flour, sugar, and salt, then gently mix to combine.

Dot the berries with small pieces of butter. Bake for 18 to 22 minutes until bubbly around the edges.

Meanwhile, prepare the topping by whisking together flour, sugar, baking powder, and salt. Melt the butter and stir in vanilla. Combine with dry ingredients until crumbly.

Crumble the topping evenly over the berries. Return to the oven and bake for an additional 20 to 25 minutes until golden brown.

Remove from oven and let cool slightly. Serve warm with ice cream or whipped cream.