• 1/4 cup unsalted butter
• 3/4 cup granulated sugar
• 1 large egg
• 2 cups all-purpose flour
• 2 teaspoons baking powder
• 1/2 teaspoon salt
• 2/3 cup whole milk
• 2 cups wild Maine blueberries

Preheat oven to 375° and butter a 9×9-inch baking pan. In a large bowl or in the bowl of a stand mixer, cream the butter and sugar together until light and fluffy, scraping the sides of the bowl with a rubber spatula as necessary. Add the egg and combine.

In a medium bowl, whisk together the flour, baking powder, and salt. Add to the creamed mixture, alternating with the milk, until well combined. Add the blueberries and fold a few times with a rubber spatula until just combined. Spread the batter evenly into the prepared pan. 

For the topping:

• 1/2 cup granulated sugar
• 1/2 cup all-purpose flour
• 1 teaspoon cinnamon
• 1/8 teaspoon table salt
• 1/4 cup cold unsalted butter, cut into cubes

In a small bowl, whisk together the sugar, flour, and cinnamon. Add the butter and combine until the mixture resembles coarse sand. Sprinkle the topping evenly over the top of the batter.

Bake until a cake tester inserted into the center comes out clean, about 40 minutes.