Whisk sugar, flour, cinnamon, and butter together in a small mixing bowl. Set aside.
For the Muffins
Preheat oven to 400°
Prepare a jumbo muffin pan by lining it with jumbo muffin liners.
In a medium bowl, whisk flour, sugar, baking powder, and salt together.
Mix egg, buttermilk, oil, and vanilla extract together than add to dry ingredients, stir.
Add lemon zest and stir just until combined, the batter will be a bit lumpy.
Gently fold in blueberries and fill liners ⅔ full.
Top each muffin with streusel topping.
Bake for 30 minutes or until toothpick inserted comes out clean.
Notes
Nutritional values are approximate.
Please note that these values can change with different brands and any modifications made to the recipe. For the most accurate information, use a nutritional calculator with the exact brands and measurements.