Step 1: In a large bowl, sift the cake flour. Then, whisk in the granulated sugar, light brown sugar, baking powder, baking soda, kosher salt, and ground cinnamon. Lastly, add in the blueberries and carefully mix to distribute.
Step 2: In a separate medium bowl, whisk together the sour cream and eggs until combined. Next, whisk in the melted butter, oil, buttermilk, and vanilla extract.
Step 3: Pour the wet ingredients into the dry ingredients and gently fold them together using a rubber spatula until just combined. Cover the bowl with plastic wrap and allow the batter to rest at room temperature for 1 hour.
Step 4: After 1 hour, preheat the oven to 425F and line a cupcake or muffin pan with 6 paper liners. Using a 3 tablespoon cookie scoop or ice cream scoop, scoop the batter into the muffin liners. Over fill each liner with the muffin batter.
Step 5: Top each muffin with a generous sprinkle of cinnamon sugar and a few extra blueberries.
Step 6: Bake the muffins for 5 minutes at 425F then lower the oven temperature to 375F and bake for an additional 15 – 18 minutes. Allow the muffins to cool for 10 minutes. Enjoy warm!!