For the crumb topping: 1/2 cup all-purpose flour 1/3 cup firmly packed light brown sugar 1/4 tsp. kosher salt 1/4 cup unsalted butter, chilled For the cake: 3 cups fresh blueberries, raspberries, or a mix 3 cups all-purpose flour more for the pan and for the berries 4 tsp. baking powder 1 tsp. baking soda…