Combine 2 cups of the cranberries and the rest of the filling ingredients in a food processor. Process until smooth. Pour into a greased pie plate. Sprinkle the remaining ½ cup cranberries on top.
Bake for 50 minutes or until the center only jiggles slightly. Cool completely.
Whip the heavy cream until peaks form. Add the sweetener and extract. Mix well. Spread on top of the cooled pie. Garnish with dried cranberries if desired.
Since this does not have a bottom crust you won't get perfect triangle slices. It's easier to just scoop some on the plate. Feel free to bake it in an 8x8 square baking dish if you prefer.