INGREDIENTS
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3 tablespoons unsalted butter, cut into 24 small pieces
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3/4 cup packed brown sugar
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2 cups frozen blueberries, thawed, drained
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Juice and grated peel of 1 medium grapefruit
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1 box Betty Crocker® French vanilla cake mix
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Vegetable oil and eggs called for on cake mix box
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1 cup frozen (thawed) Cool Whip or whipped cream
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1 tablespoon ground cinnamon