01 -
Mix brown sugar, flour, salt, and cinnamon together in a small bowl. Use your fingers to break up any sugar clumps. Work the butter in until you get a lumpy texture. Put in the fridge until you're ready to use it.
02 -
Set your oven to 375°F and make sure the rack is in the center. Coat a 9-inch square baking dish with butter or a spray that doesn’t stick.
03 -
In a medium-sized bowl, whisk salt, baking powder, and flour together. Set this aside for later.
04 -
Beat sugar and butter together until fluffy, about two minutes. Add eggs one by one, mixing thoroughly after each. Blend in the lemon zest and vanilla extract.
05 -
Slowly mix the flour mixture into the batter, switching off with splashes of milk, using a low speed. Gently stir in the blueberries so they’re evenly spread out.
06 -
Pour the batter into the greased pan and sprinkle the streusel on top. Bake for about 40 to 45 minutes, or until golden brown and a toothpick comes out clean. Let it cool in the pan for 20 minutes before slicing and plating.