
This blueberry coffee cake is soft, tender and loaded with sweet blueberries. The cinnamon streusel topping on top is buttery, crunchy and each bite melts-in-your-mouth.
Preheat the oven to 350°F. Spray an 8x8-inch baking dish (at least 2 inches deep) with nonstick spray and line with parchment paper, if desired.
In a large bowl, whisk together the oil, milk, sugar, egg, and vanilla.
Add the flour, baking powder, and salt to the bowl and mix together with a wooden spoon. Gently fold in the blueberries until just combined. Spoon the batter into the baking dish.
In a small bowl, cut the flour, cinnamon, sugar, and butter with a fork or your fingers until it forms clumps. Crumble evenly over the batter.