Preheat oven to 375 degrees F. Butter an 8 x 8 inch baking dish. Set aside.

Crumb mixture: in a large bowl, combine the flour, sugar, salt and cinnamon. Stir to combine ingredients. Add cold butter to dry ingredients.

Using a pastry cutter or two forks blend butter into the flour mixture until moist and sandy, but still clumpy. Place bowl in the refrigerator.

Cake: In a medium bowl combine the flour, baking powder and salt. Whisk to combine; set aside.

In a large mixing bowl, mix the butter and sugar with paddle attachment, until light and fluffy.

Add the egg and vanilla. Mix until combined.

Add half of the dry ingredients and mix until just combined, then add in buttermilk, followed by the remaining dry ingredients. Mix until just incorporated.

Using a rubber spatula, fold the blueberries into the batter.

Place batter into butter baking dish and smooth the top.

Take crumb mixture; gently break up large crumbs and scatter mixture evenly over the batter.

Bake for 40-45 minutes or until a toothpick inserted into the center comes out clean.

Let cool, then cut into squares and serve. Enjoy!