Heat oven to 350 degrees.
Add gluten free graham crumbs and melted butter to square dish.
Stir to mix and then spread evenly and also pat down for an even crust.
Place dish in oven for 8-10 minutes.
Remove from oven and let crust cool.
For filling, beat cream cheese until smooth, then slowly add sugar and vanilla.
Beat mixture until well blended.
In a clean bowl, beat the whipping cream until soft peaks form.
Slowly beat the whipped cream into the cream cheese mixture.
Spoon the cream cheese/whipping cream mixture onto the cooled graham crust.
Smooth filling onto crust.
For berry topping, in a large saucepan heat 3 cups Saskatoon berries with 2 ½-3 cups water until mixture starts to come to a boil.
Reduce heat to medium.
In a small bowl mix the 3 Tbsp cornstarch with 3 Tbsp cold water.
Stir until smooth.
Add cornstarch mixture to hot berries and slowly stir until mixture thickens.
Remove from heat and let cool.
Berries will thicken further as they cool.
Once cool top cream cheese mixture with berries.
Cover with saran wrap and completely cool in refrigerator.
Slice and serve.