Preheat oven to 350 degrees
Line an 8x8 pan with parchment paper & then lightly spray paper with cooking spray
In mixer bowl, combine butter & SPLENDA Naturals until light & fluffy
Beat in vanilla & eggs until fully incorporated
Slowly add in flour, cornmeal, baking soda, baking powder & salt along with buttermilk & beat well
Add half the batter to the bottom of the prepared pan
Sprinkle some of the topping mixture over the batter
Sprinkle some of the blueberries on top
Fold the remaining blueberries into the remaining batter in the bowl & then add batter to the pan
Sprinkle with topping in an even layer
Add walnuts if desired
Bake 55-65 minutes or until toothpick test comes out clean