Preheat oven to 375 degrees F.
Prepare a greased and floured 9” cake pan.
For the topping: Mix sugar, flour, and cinnamon in a small bowl. Cut in butter until crumbly. Set topping aside.
For the batter: Whisk flour, baking powder, and salt in a medium-sized bowl.
In another bowl, cream sugar, butter, egg, and vanilla on medium speed using a handheld mixer or standing mixer.
Add the milk and flour alternately to the creamed mixture in 1/3’s, ending with the flour and making sure not to overmix.
Fold in the berries. Pour batter into pan.
Sprinkle topping over batter.
Bake 40-45 minutes, or until a cake tester or toothpick comes out clean. Allow to cool slightly and remove from pan. Do not over-bake!