In a large bowl, cream together ¼ cup butter, ¾ cup white sugar and egg.
In a another bowl, combine 1⅔ cup flour, baking powder and salt. Stir flour mixture gradually into sugar mixture, mixing alternating with milk and vanilla extract. Stir in blueberries. Spoon batter into prepared baking pan.
Crumb Topping
In a bowl, combine ½ cup brown sugar, ¼ cup flour and cinnamon. Cut in ¼ cup butter. Sprinkle crumb mixture over batter.
Bake for 45 minutes, or until done.
Recipe by Sugar, Spice and Family Life at https://sugarspiceandfamilylife.com/2015/01/blueberry-buckle-recipe.html