Classic Sunday Coffee Cake

Preheat the oven to 350 degrees F. Grease and flour a 9-inch pie pan.

FOR THE BATTER:
In a large bowl, cream the butter and sugar until light and fluffy. Add the egg, vanilla, and orange zest, and beat well. Stir together the flour, baking powder, baking soda, and salt, and add the dry ingredients along with the buttermilk, mixing just until the batter is smooth and thick. Mix in the fruit and spread in the prepared pan.

FOR THE STREUSEL TOPPING:
In a bowl, combine the flour, butter, sugar, and cinnamon, mixing until crumbly; mix in the chopped nuts. Sprinkle over the top of the batter and stud with nut halves. Bake for 40 to 45 minutes, or until a toothpick inserted in the center comes out clean. Serve warm, cut into wedges.