Using an electric mixer if you have one, cream the butter and sugar together well. Add the eggs, one at a time, beating well after each addition. Sift the flour with the baking powder, orange zest and salt and add the mixture gradually to the butter mixture.
Combine the yogurt and baking soda and add to butter a few tablespoons at a time, along with the vanilla. Add the raisins, spices and walnuts and mix just until they are well combined in the cake batter.
Pour the batter into a 9-inch square pan. Bake at 350°F for 40 minutes.
Makes 9 to 12 servings.
Notes
Optional Orange Glaze
This recipe doesn't call for icing, but a light glaze would be very nice on top. If you want to make a glaze for the cake, use icing sugar, enough orange juice to moisten it and a drop of almond flavoring (optional). Make the mixture thin enough that you can drizzle the icing on top of the cake. You don't need much as it's a small cake. I would start with 1/4 cup of icing sugar.