Dry:
3 1/2 cups all-purpose flour
5 tsp baking powder
1/2 tsp baking soda
1 1/2 tsp salt
1 cup sugar
2 cups fresh blueberries
Wet:
1 1/2 c buttermilk
2/3 c vegetable oil
2 eggs, lightly beaten
Preheat oven to 375F and lightly grease a 9x13 pan.
Combine dry ingredients in a large bowl. Add blueberries, tossing gently. Make a well in the center of the mixture. Whisk wet ingredients together in a different bowl, then add all at once to flour mixture, stirring just until moistened.
Spoon batter into prepared pan and top with streusel. Bake in preheated oven until a toothpick inserted into the center comes out clean, about 40 minutes. Cool cake in pan on a wire rack.
Streusel topping: 1/4 c sugar, 2 1/2 Tbsp flour, 1/2 teaspoon cinnamon, 1 1/2 Tbsp butter (Mix sugar, flour, and cinnamon. Cut in butter with pastry blender until mixture is crumbly.)
