Blueberry Buckle
["1/2 c. (1 stick) unsalted butter (plus more for pan)", "2 c. flour (plus more for pan)", "1 1/2 tsp. baking powder", "1/2 tsp. salt", "3/4 c. sugar", "1 egg", "1 tsp. vanilla", "1/2 c. milk", "5 c. blueberries", "1 recipe Streusel Topping (recipe follows)"]
["Preheat oven to 350\u00b0.", "Butter and flour spring-form baking pan; set aside.", "Sift together flour, baking powder and salt; set aside.", "With electric mixer on medium, cream butter and sugar until light and fluffy, about 3 minutes.", "Reduce speed to low and add egg and vanilla.", "Alternately add flour mixture and milk, beginning and ending with flour mixture.", "Fold in berries."]
["unsalted butter", "flour", "baking powder", "salt", "sugar", "egg", "vanilla", "milk", "blueberries", "Streusel"]