Preheat oven to 375°F. Lightly grease a 9x9-inch square pan.
Melt margarine, stir in brown sugar and cinnamon, and set aside. Sift together flour, baking powder, sugar, and salt in a large bowl. Cut in shortening with a pastry blender until size of small peas. Make a well in the center (volcano). In another bowl, slightly beat egg with a whisk. Add in milk and vanilla. Add the liquid ingredients to the well, and mix until moistened.
Put batter evenly into cake pan. Sprinkle cinnamon topping over. Bake for 30-35 minutes.