Preheat oven to 375 degrees F. Lightly grease 8x8-in. pan.

In small bowl mix together sugar, flour, cinnamon and salt for streusel.

Using fork, mash and mix in butter until crumble forms. Set streusel aside. (Note: Do not over mix.)

In stand mixer bowl, combine sugar, butter, egg and lemon zest. Beat until cream forms.

In medium bowl combine flour, baking powder and salt.

Slowly add flour mixture and milk into creamed sugar/butter mixture and beat with stand mixer until combined.

Lightly dust blueberries with flour and add to mix; Fold until evenly incorporated throughout batter. (Note: Dusting blueberries with flour keeps them from sinking to bottom of pan.)

Pour batter into pan and sprinkle streusel over top.

Bake 45 minutes or until toothpick inserted in center comes out clean.

Remove from oven and rest 10 minutes. Cut into squares to serve.