Fluffy lemon cupcakes with swirls of blueberry syrup topped with lemon frosting with a blueberry swirl

2/3 cups blueberries

1/3 cup granulated sugar

pinch of salt

1 1/2 cups cake flour (can also use unbleached all-purpose flour)

1 1/2 teaspoons baking powder

3/4 teaspoon salt

1/2 cup  unsalted butter, room temperature

1 cup granulated sugar

zest of two lemons

2 large eggs, room temperature

1 1/2 teaspoons vanilla extract

1/2 cup buttermilk, room temperature

3 tablespoons fresh lemon juice

12 teaspoons bluberry sauce

1/2 cup unsalted butter, room temperature

3 1/2 cups powdered sugar

zest of half a lemon

1 - 2 tablespoons blueberry sauce

2 - 3 tablespoons heavy cream