sweet potato-pecan coffee cake

Ingredients

• 1/2 cup plus 2 tablespoons butter or margarine melted
• 3/4 cup sugar
• 2 - large eggs
• 2 teaspoons vanilla
• 1 cup sour cream
• 3/4 cup mashed, cooked sweet potatoes
• 2 cups all purpose flour
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt (optional)
• 1 teaspoon cinnamon
• TOPPING
• 1 cup chopped pecans
• 1/2 cup brown sugar
• 1/2 cup flour
• 3 tablespoons butter or margarine softened
• 1 teaspoon cinnamon
• 2 teaspoons vanilla