Cream together butter and sugar until pale yellow and creamy. Add egg and vanilla and beat in.
Sift together flour, baking powder and salt. Add alternately with milk until incorporated. Scrape batter into cake pan and spread evenly. Sprinkle blueberries on top of batter.
Topping
In small bowl blend sugar, flour and cinnamon. Cut in butter with your fingers until crumbly and no large bits of butter are visible. Sprinkle on top of berries.
Bake for 45-50 minutes. Allow to cool before serving.
Recipe by gabriela cuisine at https://gabrielacuisine.ro/blueberry-buckle-chec-pufos-cu-afine/