Preheat oven to 425 degrees. Spray a standard muffin tin with baking spray or line with paper liners.
For the streusel:
In a small bowl combine the melted butter, granulated sugar, brown sugar, lemon zest, and flour with a fork until crumbly. Refrigerate until ready to use.
For the muffins:
In a medium bowl combine flour, baking powder, and salt.
In a large bowl whisk 1 cup of sugar and 2 eggs until thick and pale. Slowly add the vegetable oil and melted butter, mix until combined.
Add the buttermilk and vanilla, mix until combined. Gently fold the egg mixture, flour mixture, and blueberries together just until combined (careful to not over mix, it will be lumpy with some dry flour spots).
Using ice cream scoop divide the batter among 12-18 muffin cups.
Evenly divide the streusel among muffin tops.
Bake for 17-18 min. Let muffins cool in the muffin tin for 5 minutes. Transfer to a wire rack to continue cooling.