If using a medium sized muffin pan without liners, grease the bottoms of each cup.
In a small bowl mix together brown sugar, granulated white sugar, flour, and lemon zest with a fork. Cut in butter until mixture looks like medium grain rice. Set aside for later.
In a medium sized bowl beat together oil, sugar, egg, milk, and lemon zest with a fork.
Sift together flour, baking powder and salt. Reserve one tablespoon of flour mixture.
In a separate small bowl combine 3/4 cup blueberries with the reserved 1 tablespoon of flour mixture. Set aside dredged blueberries.
Add the flour mixture all at once into the wet ingredients. Using a rubber spatula gently fold the flour into the wet ingredients but mix only until batter is barely mixed. Streaks and clumps of flour/dough should still be visible.
Gently fold dredged blueberries into batter.
Fill baking cups ½ full. Top the center of each muffin with reserved blueberries and follow with streusel topping. Bake in oven 20 to 25 minutes
• All ingredients should be at room temperature. Since the batter will continue to be mixed when the blueberries are added, it is important not to overmix the batter before their addition.• Lemon pairs deliciously with blueberries. But, if you do not have a lemon on hand to zest, you can omit the lemon zest from the batter and substitute 1 tablespoon of cinnamon for the lemon zest in the streusel topping.• Some bakers add ½ teaspoon of vanilla to the batter for extra richness of flavor.• When adding blueberries to the top of the muffins, be sure to add them away from the edges of the baking cups. Blueberries near the edge of the pan or liner may burst and make it more difficult to remove the muffins from the pan and liners.• Muffins are best eaten day of bake. But can be stored in an airtight container up to 3 days. Gently warming muffins will bring out the flavor, if serving them in the days after the bake.