Buttermilk Coffee Cake
["1 stick unsalted butter, cut in bits and softened", "1 c. granulated sugar", "2 large eggs", "2 c. all-purpose flour", "1 tsp. baking soda", "1 tsp. baking powder", "1/2 tsp. salt", "1 c. buttermilk", "1 tsp. vanilla", "1/3 c. firmly packed dark brown sugar", "1 tsp. cinnamon", "1/2 c. chopped pecans or walnuts"]
["Beat the first 9 ingredients in a large bowl with an electric mixer until smooth and fluffy.", "Make a topping of the brown sugar, cinnamon and chopped pecans or walnuts."]
["unsalted butter", "sugar", "eggs", "flour", "baking soda", "baking powder", "salt", "buttermilk", "vanilla", "brown sugar", "cinnamon", "pecans"]