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