INGREDIENTS
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oven to 350
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for the streusel:
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1/2 cup firmly packed light brown sugar
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1 cup hazelnuts
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1 tsp cinnamon
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4 Tbsp cold unsalted butter
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1/2 tsp vanilla extract
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for the batter:
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1 stick, 8 Tbsp unsalted butter, room temperature
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1 cup sugar
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2 large eggs
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1/2 cup sour cream
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1 tsp vanilla extract
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1 cup cake flour
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1 cup hazelnut flour (finely ground hazelnuts)
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1 tsp baking powder
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1 tsp baking soda
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1/2 tsp salt