Moist, fluffy cake with blueberries in every bite, topped with a delicious streusel topping.
Preheat the oven to 350° F and spray a 9 x 13 inch pan with non-stick cooking spray. Mix all ingredients together except blueberries in a medium bowl. Mix for 30 seconds on low and then 2 minutes on high.
Divide the batter in half and spread one half in an even layer in the prepared pan. It might seem like it will not be enough. Just keep spreading as best you can into one thin, even layer.
Sprinkle the blueberries* over the batter. Add the other half of the batter in spoonfuls over the blueberries. Spread out evenly trying to cover the all the berries. It is okay if they peak through, do the best you can!
Combine the ingredients for the topping in a small bowl. Mix with the back of a fork until it is combined and crumbly. It will take a few minutes to get it all mixed. You do not want to see any flour. Bake for 30-40 minutes until a toothpick comes out clean. Serve warm.
*I have made this cake with a triple berry mix (strawberries, blackberries, and raspberries) and my family liked it even more. Apples would be delicious as well - be creative!