Preheat oven to 425 degrees f. Spray a 6-cup large-sized muffin tin lightly with cooking spray, set aside.In a small bowl combine the lemon zest and 1/3 c. sugar, using a fork, mix thoroughly.In a large bowl combine flour, baking powder and salt. In a medium bowl, combine 1 c. sugar and eggs, whisking vigorously for about 45 seconds, until the mixture is thick and homogeneous. Slowly add in melted butter and oil. Then whisk in buttermilk and vanilla.
Add the liquid ingredients and the blueberries to the dry ingredients, folding until just mixed, taking care to not over mix. Scoop batter into the muffin tins and sprinkle the tops with the lemon-sugar.
Bake the muffins at 425 degrees f. for 5 minutes then reduce the heat to 375 degrees f. and continue baking for about 25 minutes (rotating the pan halfway through the bake time to ensure even baking), until a toothpick inserted near the center of the muffins comes out clean with only a few crumbs attached.
Let the muffins cool for about 5 minutes in the pan before removing them to a wire rack to cool.
