1. Preheat the oven to 425 degrees. Line a muffin tin with cupcake liners. In a medium bowl, combine the softened butter, brown sugar, sugar, all purpose flour and cinnamon together until crumbly. Set aside. 2. In a medium bowl, sift together the flour, baking powder and salt. Remove a teaspoon of flour and coat the blueberries with it. Set Aside.3. In a stand mixer, mix together the lemon zest, sugar and softened butter for about 2 minutes. Add in egg one at a time, then vanilla and mix.4. Next, add in the flour and milk in stages, alternating between the two, starting and stopping with flour. Fold in the floured blueberries. 5. Scoop the muffin batter into the liners, filling about 3/4 of the way. Spoon the streusel over the top of the batter. Bake at 425 degrees for 5 minutes then lower the temp back down to 350 degrees and bake for 18-20 minutes. 6. Serve with softened butter or by itself and enjoy!