Heat oven to 350°F. Spray a 13x9-inch baking pan with nonstick cooking spray.
Crumb Topping: In a large bowl, combine brown sugar and flour. With two forks or pastry cutter, cut butter into the flour mixture until crumbly. Stir in walnuts. Set aside.
Coffee Cake: With an electric mixer on high, beat butter and granulated sugar until creamy, about 1 minute. Gradually beat in sour cream, eggs and vanilla.
Reduce speed to low and beat in flour, baking powder, baking soda and salt.
Spread mixture in the prepared baking pan and sprinkle with crumb topping.
Bake 45 to 50 minutes or until toothpick inserted in the center comes out clean.
Heat oven to 350°F. Spray a 13x9-inch baking pan with nonstick cooking spray.
Crumb Topping: In a large bowl, combine brown sugar and flour. With two forks or pastry cutter, cut butter into the flour mixture until crumbly. Stir in walnuts. Set aside.
Coffee Cake: With an electric mixer on high, beat butter and granulated sugar until creamy, about 1 minute. Gradually beat in sour cream, eggs and vanilla.
Reduce speed to low and beat in flour, baking powder, baking soda and salt.
Spread mixture in the prepared baking pan and sprinkle with crumb topping.
Bake 45 to 50 minutes or until toothpick inserted in the center comes out clean.