I’ve been making this blueberry cake for years. It works well as either a coffee cake or made into muffins.
1 Preheat oven to 375 degrees F (190 degrees C). Grease and flour a 9 inch pan. Sift together the flour, baking powder and salt. Set aside.
2 In a large bowl, whisk together the oil, sugar and egg. Stir in the flour mixture alternately with the milk, mixing just until incorporated. Fold in the blueberries. Pour batter into prepared pan. Cover with streusel topping.
3 For the topping: In a bowl, combine 1/3 cup flour, cinnamon and 1/2 cup sugar. Cut in the butter until mixture resembles coarse crumbs.
4 Bake in the preheated oven for 45 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool.