"Make Martha Stewart's Caramel Buttercream Layer Cake featured in the Sponge Cake episode of Martha Bakes...."
INGREDIENTS
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Unsalted butter, for pans
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3/4 cup all-purpose flour, plus more for pans
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3/4 cup cornstarch
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6 large eggs, separated
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1 1/2 teaspoons pure vanilla extract
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3/4 cup plus 6 tablespoons sugar
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1/4 teaspoon salt
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For Caramel Buttercream Frosting:
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2 1/4 cups sugar
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1/2 cup heavy cream
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9 large egg whites
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3/4 teaspoon salt
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3 cups (6 sticks) unsalted butter, softened
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1 1/2 teaspoons pure vanilla extract