Preheat oven to 350 degrees. Prepare an 8x8 inch pan with non-stick spray.
In a large bowl, cream together the butter, sugar and lemon zest until the mixture is light and fluffy. Add in the egg and vanilla and mix until combined.
In a medium bowl, mix together the flour, salt and baking powder.
Pour part of the flour mixture into the large bowl of wet ingredients, stir, add in the plain yogurt and rest of flour mixture and then mix until completely combined. Next fold in the blueberries.
Spread the batter into your prepared pan, batter will be thick, and sprinkle the top with a little bit of sugar.
Bake for 40-45 minutes, until a toothpick comes out clean.
Cool for 10-15 minutes before cutting and serving. Lightly cover with foil and store on the counter.
Prepare the glaze by mixing together the powdered sugar and heavy cream, start with 2 tbsp of cream and continue to add more until the desired consistency has been reached.
Drizzle all over the top and sprinkle a little lemon zest on top.