Preheat the oven to 400°F. Line a 12-cup muffin pan with liners. Alternatively, you can spray the wells with nonstick cooking spray, set aside.
In a medium bowl, combine the flour, granulated sugar, brown sugar, and cinnamon. Pour in the melted butter and stir until the mixture resembles coarse, sand-like crumbles. Then set aside.
In a medium bowl, combine the flour, baking powder, and salt, and whisk the dry ingredients well to thoroughly combine and set aside.
In a large bowl, combine the eggs, granulated sugar, oil, sour cream, and vanilla, and whisk the wet ingredients. Add the flour mixture into the bowl and mix until just combined with no remaining flour streaks.
Then gently fold the blueberries into the muffin batter.
Use a large, spring-loaded ice cream scoop or spoon to fill the muffin liners with an even amount of batter, filling each all the way to the top.
Sprinkle a generous amount of streusel topping onto the top of each muffin, gently pressing it down so it sticks. Place the muffins into the oven and reduce the heat to 375°F.
Bake the muffins for 20-25 minutes or until a toothpick inserted into the center of the muffin comes out clean. Let the muffins cool for 5 minutes and then transfer to a wire rack to continue cooling.