Sour Cream Coffee Cake

1 cup sour cream 2 eggs, well beaten 1 teaspoon baking soda 1 stick butter, room temperature 1 cup sugar 1 teaspoon vanilla 2 teaspoon baking powder 1¾ cups flour TOPPING: ¼ cup brown sugar 1 tablespoon cinnamon 2 tablespoon chopped walnuts or pecans

Preheat oven to 350F. Grease and flour an 8 inch pan. Combine sour cream and baking soda in a bowl. Blend butter and sugar; beat in vanilla and eggs. Beat in dry ingredients and sour cream until smooth. Spread half the batter in prepared pan. Sprinkle with half the topping. Bake for 45-50 minutes. Serve warm.