Your guests will never guess that this creamy, velvety cheesecake is lower in fat and calories.
Propane gas torches are highly flammable and should be kept away from heat, open flame and prolonged exposure to sunlight. They should be used only in well-ventilated areas. Follow torch manufacturer's instructions for use.
Position the oven racks in center and lower third of your oven. Fill a roasting pan about half full of water and place on the lower rack. This will create a moist environment for the cheesecake and help prevent cracking. Preheat the oven to 325ºF.
Coat a 9-inch springform pan with nonstick cooking spray. Put the graham crackers and 1 tablespoon of granulated sugar in the bowl of a food processor and grind until fine. Add the butter and two tablespoons of water and pulse until moistened. Press into the bottom of the prepared springform pan. Bake until set and golden brown, about 10 minutes. Cool completely.
Combine the cream cheese, brown sugar, 1/3 cup granulated sugar and salt in a large bowl. Beat, with an electric mixer on medium speed, until smooth and fluffy. Add the yogurt, egg and egg whites, reduce the mixer speed to low, and continue to beat until blended. Add the pumpkin, flour, vanilla and pumpkin pie spice. Reduce the mixer speed to low and beat until just combined. Stir with a spatula a few times to make sure all the ingredients are incorporated and to release any air bubbles in the batter that could cause the cheesecake to crack.
Pour the batter over the crust and rap the pan against the countertop a few times to bring any trapped air bubbles to the surface. Place the cheesecake on the center rack in the oven. Bake until just set and the center wiggles slightly, about 1 hour to 1 hour and 10 minutes. Turn the oven off and crack the door open. Let sit in the oven for 15 minutes and then transfer to a wire rack to cool. Run a thin sharp knife between the cheesecake and then pan to release the sides. Cool completely and then chill until cold, at least 4 hours, or overnight.
Before serving, remove the cheesecake from the refrigerator and release the sides of the pan. Sprinkle the remaining 2 tablespoons sugar over the top of the cheesecake and brulee the sugar with a kitchen torch or under the broiler for a few seconds.