Blueberry Buckle

INGREDIENTS

• 1/2 cup (1 stick) unsalted butter, room temperature, plus more for pan
• 2 cups all-purpose flour, plus more for pan
• 1 1/2 teaspoons baking powder
• 1/2 teaspoon salt
• 3/4 cup sugar
• 1 large egg
• 1 teaspoon pure vanilla extract
• 1/2 cup milk
• 5 cups wild or cultivated blueberries
• Mrs. Kostyra's Streusel Topping