1 box of yellow cake mix
¾ cup oil
1 cup sour cream (I used 1 cup of yogurt + 1 teaspoon of baking soda)
1 cup brown sugar
1 tablespoon cinnamon
2 cups powdered sugar, sifted
2-4 tablespoons milk
Preheat oven to 325F and grease a 13x9-inch baking pan.
Mix the first four ingredients by hand and pour into the prepared pan.
In a small bowl, combine the brown sugar and cinnamon and sprinkle it over the cake batter. Swirl decoratively with a knife.
Bake for 40-50 minutes and let it cool briefly before adding the icing.
To make the icing, stir together the sugar and milk until smooth, adding more milk as needed. Pour over the warm cake.