Coffee Cake:

2 c. all purpose flour
1/2 tsp. salt
1 tsp. cinnamon
1 tsp. baking soda
1 tsp. baking powder
1 c. sugar
1/2 c. brown sugar
2/3 c. butter
2 eggs
1 c. plain yogurt (or buttermilk)
1 tsp. vanilla

Topping:

1/2 c. brown sugar
1/2 tsp. cinnamon
1/4 tsp. nutmeg
1/2 c. chopped walnuts

Cake:

In a large bowl, cream together butter and sugar. Add eggs, one at a time, beating well after each addition.

In a medium bowl, combine flour, salt, cinnamon, baking powder, baking soda, and 1 cup granulated sugar. Mix well. Stir in brown sugar and mix well.

Melt butter, allow to cool and stir in yogurt. Add the butter and yogurt mixture alternately with the flour mixture to the large bowl (with the butter, sugar and eggs). Stir in vanilla; turn batter out into a greased 9x13-inch pan.

Topping:

Combine ingredients for topping and sprinkle over the top of batter.

Refrigerate for up to 12 hours before baking. Batter may thicken slightly; stir in a small amount of milk if needed to thin batter.

Bake in a preheated 350°F oven until a wooden pick inserted in center of cake comes out clean (about 35 minutes).