Preheat your oven to 350 degrees. Grease the bottom and sides of a 9 x 9 square or 10” round baking pan.
In a small bowl, combine the 2 cups of flour, baking powder and salt. Set aside.
In a small bowl, combine the brown sugar and cinnamon for the filling. Stir well and set aside.
In a medium bowl, combine the brown sugar, flour and cinnamon for the topping. Stir well to combine, then gradually add the melted butter until it resembles damp sand. Set aside.
In a large bowl, cream the sugar and butter with a hand mixer. Add the eggs and continue to mix. Add the ½ & ½ and vanilla. When all is combined well, add the flour, baking powder and salt mixture. Mix at a low speed until all of the dry ingredients are mixed in, then scrape the bowl and continue mixing for another minute until it is smooth & creamy.
Pour half of the batter into the bottom of the baking pan and smooth it out from edge to edge with a spatula. This will be a pretty thin layer… only about ½ inch thick. Sprinkle the filling mixture evenly on top.
Pour the remaining batter on top of the filling and carefully spread it out in an even layer. Sprinkle evenly with the topping mixture.
Bake for 45-50 minutes until the center no longer is soft and jiggly. Watch it closely after 40 minutes so that it doesn’t get over baked.
Remove from the oven and let cool. Once cooled to room temp, it can be inverted onto a serving plate and cut for serving. Serve with coffee, tea, whipped cream or ice cream.