Blueberry Cupcakes

INGREDIENTS

• 6 tablespoons granulated sugar
• 1/4 cup dark-brown sugar
• 1 teaspoon cinnamon
• 1 2/3 cups cake flour (not self-rising)
• 1/4 teaspoon baking soda
• 1 teaspoon baking powder
• 1/2 teaspoon salt
• 1 stick unsalted butter, softened
• 2/3 cup granulated sugar
• 2 large eggs
• 1 teaspoon pure vanilla extract
• 3/4 cup sour cream
• 6 ounces blueberries (1 1/4 cups)
• 1 1/4 sticks unsalted butter, softened
• 8 ounces cream cheese, room temperature
• 1/2 teaspoon pure vanilla extract
• 2 2/3 cups confectioners' sugar, sifted
• 1/4 cup high-quality blueberry jam, such as Hero, strained (3 tablespoons)