Lemon Blueberry Cake

My lemon blueberry cake is bursting with beautiful natural flavors and so refreshing! This moist easy to make cake is filled with delicious blueberry and lemon buttercream. Its one of my most popular cakes and a personal favorite so I hope you get a chance to bake one up!
Ingredients
For the Cake
1 ¾ cup all purpose flour 210g plus 1 tbsp to coat berries
1 ½ tsp baking powder
¼ tsp kosher salt
1 23 cup granulated sugar 333g
34 cup unsalted butter 170g room temperature
3 egg whites room temperature
12 cup whole milk 120ml room temperature

12 cup sour cream 120ml room temperature
⅓ cup lemon juice 60g fresh
1 tbsp lemon zest
1 tbsp vanilla extract 15mL
1 13 cup blueberries 180g fresh
For the Reduction
1 tbsp water 15mL
1 12 cup blueberries 203g fresh
1 tbsp granulated sugar
1 tbsp lemon juice fresh
For the Lemon Buttercream
1 12 cups unsalted butter 339g room temperature
6 cups confectioners sugar 720g
3 tbsp lemon juice 45g
14 tsp kosher salt
Instructions
For the Cake
Preheat oven to 340 degrees F. Butter and flour three 6inch pans. I use damp cake strips on my pans for more even baking as well.
Sift the dry ingredients including the sugar together in a large bowl.
Beat the wet ingredients together in a medium bowl.
In a small bowl add blueberries and lemon zest. Coat with about 12 tbsp flour.
Add the wet to the dry and mix until just combined. Fold in blueberrylemon zest at the very end and mix until just combined.
Divide the mixture evenly into the cake pans.
Bake at for about 30 minutes or until the