Ingredients:

• 1 1/3 cups (182g) all-purpose flour plus 1 teaspoon for dusting the blueberries
• 1 1/4 teaspoons baking powder
• 1/2 teaspoon baking soda
• 1/2 teaspoon kosher salt
• 4 tablespoons (56g) unsalted butter, softened
• 1/2 cup plus 2 tablespoons (135g) granulated sugar
• 1 1/4 teaspoons vanilla extract
• 1 large egg, at room temperature
• 4 teaspoons neutral oil, such as canola or vegetable
• 1/2 cup low-fat buttermilk, at room temperature
• 1 1/3 cups (7 1/4 ounces) fresh blueberries, washed and well dried
• For the streusel and finishing
• 2/3 cup (85g) all-purpose flour
• 1/3 cup (37g) rolled oats
• 1/3 cup (65g) light brown sugar, tightly packed
• 1/2 teaspoon kosher salt
• 4 tablespoons (56g) unsalted butter, melted
• 1/2 teaspoon vanilla extract
• Powdered sugar, as needed for dusting (optional)