This lemon blueberry coffee cake is a refreshing twist on the classic recipe. The cake is moist and fluffy, with a layer of blueberries running through the middle and on top. The lemon adds a tangy flavor that balances out the sweetness of the blueberries. The streusel topping is made with brown sugar, cinnamon, and butter, giving it a crunchy texture and a rich, buttery flavor. This coffee cake is perfect for a summer brunch or a lazy weekend breakfast.