Preheat oven to 350° F and grease an 8x8 square baking dish with butter or spray oil.
Making the crumb topping
Add the flour, brown sugar, white sugar, and cinnamon to a small mixing bowl and mix together.
Add the diced cold butter to the flour mixture and cut it into the flour mixture using a fork or two knives. Make sure all of the flour and sugar mixed and it becomes moist and crumbly. I have even used my hands.
Making the Cake
In a medium mixing bowl, combine the flour, sugar, baking powder, cinnamon and salt and mix well.
Add the butter to the dry ingredients and blend well.
Add the milk, egg, and vanilla extract and stir until just barely blended and the
Pour half of the cake batter into the baking dish and sprinkle a thin layer of the crumb topping across the batter.
Then pour the remaining batter in and spread evenly.
Top with the remaining streusel topping and again spread evenly across the top.
Baking the Coffee Cake
Bake for 40 minutes or until a toothpick comes out clean when inserted into the center.
Cool for 5-10 minutes before slicing into 9 squares.
Add ¼ -⅓ cup of chocolate chips to the batter.Add in ½ cup of fresh diced apples or fresh blueberriesAdd in nuts like chopped pecan or chopped walnuts to the streusel topping.Use sour cream or plain Greek yogurt in place of milk Swap out the butter in the cake for an equal amount of unsweetened applesauce for a lower calorie cake.Use almond milk , soy milk or any other non-diary milk. Vanilla flavored milk will also be good.Use gluten free flour like Bob's red Mill One-to-One.Double the recipe and bake in a 9x13 rectangle baking dish Store in an airtight container for a couple of days on the countertop or for up to a week in the refrigerator. I like to put mine in the microwave for about 10 seconds to warm it up just a tad before eating.