In a mixer, combine Parkay, sugar and eggs. Add baking powder, vanilla, milk, and slowly add the flour. Mix until smooth. Grease a 9 x 13 x 2 cake pan. Spread half of the dough in the pan. Sprinkle the top with brown sugar, cinnamon, and dot with butter. Pour the rest of the batter in, then sprinkle with brown sugar, cinnamon, and dot with butter again. Bake at 350 degrees for 30-35 minutes. Test with a toothpick for doneness.