Preheat your oven to 325°F. Wrap the outside of a 9-inch springform pan tightly with two layers of aluminum foil to prevent water from seeping in during the water bath.
In a medium bowl, mix the gluten free graham cracker crumbs, melted butter, and sugar until evenly combined. Press the mixture firmly into the bottom of the prepared springform pan using the flat bottom of a measuring cup. Bake for 10 minutes, then remove and let it cool while you prepare the filling.
In a large bowl, beat the cream cheese and sugar with an electric mixer on medium speed until completely smooth, about 3 minutes. Scrape down the sides of the bowl as needed to avoid any lumps.
Add the ube halaya and ube extract, beating until the color is uniform and vibrant purple throughout. Add the cornstarch and vanilla extract and mix until just combined.
Add the eggs one at a time, beating on low speed after each addition until just incorporated. Do not overmix. Fold in the sour cream by hand with a spatula until smooth.
Pour the filling over the cooled crust. Place the springform pan inside a large roasting pan and carefully pour hot water into the roasting pan until it reaches halfway up the sides of the springform pan. Bake for 55 to 60 minutes, until the edges are set but the center still has a slight jiggle.
Turn off the oven, crack the oven door open a few inches, and let the cheesecake cool inside the oven for 1 hour. Then remove it from the water bath, discard the foil, and refrigerate for at least 6 hours or overnight.
When ready to serve, whip the heavy cream, powdered sugar, and ube extract together until stiff peaks form. Spread or pipe over the chilled cheesecake, then sprinkle with crushed freeze-dried raspberries for garnish.