Ingredients:

Filling

• 1/2 cup brown sugar
• 2 Tbsp butter
• 1/2 cup finely chopped nuts (optional)
• 3/4 tsp ground cinnamon

Cake

• 3 cups flour
• 1 1/2 tsp baking powder
• 1 1/2 tsp baking soda
• 3/4 tsp salt
• 1 1/2 cup sugar
• 3/4 cup butter, softened
• 1 1/2 tsp vanilla
• 3 large eggs
• 1 1/2 cup sour cream or plain yogurt

Glaze

• 1 cup powdered sugar
• 3-4 tbsp milk
• 1/2 tsp vanilla

Directions:

1. Preheat oven to 325°. Grease and flour one 12 cup tube pan.
2. Combine filling ingredients and mix until crumbly. Set aside.
3. Combine flour, baking powder, baking soda, and salt in a bowl.
4. In a large bowl, cream butter, sugar, vanilla, and eggs. Continue to beat on medium speed for 2 minutes. 
5. Add flour and sour cream alternately, 1/3 at a time, beating on low speed until ingredients are combined.
6. Pour 1/3 of the batter (about 2 cups) into the well-greased tube pan. Sprinkle with 1/3 of the filling. Repeat to create 3 layers.
7. Bake for 1 hour (may take longer in some ovens), until a toothpick inseted into the center comes out clean.
8. Cool in the pan for 10 minutes. Using a knife, separate the cake from the pan around the outside edge.
9. Combine glaze ingredients. Beat until smooth. Drizzle over coffee cake. Serve warm or cool.