Sour Cream Coffee Cake

1 cup sour cream 2 eggs, well beaten 1 tsp baking soda 1 stick butter, room temperature 1 cup sugar 1 tsp vanilla 2 tsp baking powder 1 3/4 cups flour TOPPING: 1/4 cup brown sugar 1 tbsp cinnamon 2 tbsp 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.