A classic pumpkin cheesecake should be creamy, perfectly spiced and totally smooth on top. While baking a cheesecake in a water bath may seem like a pesky extra step, it keeps the cheesecake luscious and crack-free.
Preheat the oven to 325˚ F. Wrap the outside (bottom and sides) of a 9-inch springform pan with foil to prevent leaking. Make the crust: Toss the graham cracker crumbs, melted butter and sugar in a bowl until combined. Firmly press into the bottom of the pan. Bake until set and a few shades darker, about 10 minutes. Transfer to a rack to cool completely.
Bring a kettle of water to a boil. Make the filling: Beat the cream cheese in a large bowl with a mixer on medium-high speed until smooth, about 2 minutes. Add the sugar and beat until light and fluffy, about 3 more minutes. Add the pumpkin, sour cream, pie spice, vanilla and salt and beat until combined. Add the eggs and beat on medium-low speed until just combined; switch to a rubber spatula for the last few stirs, making sure to get the bottom of the bowl. Pour the filling into the cooled crust; gently tap the pan on the counter a few times to release any air bubbles.
Set the cheesecake in a roasting pan or large baking dish and set on the middle oven rack. Carefully pour the boiling water into the roasting pan until it comes one-third of the way up the sides of the springform pan. Bake the cheesecake until it’s set around the edges but the center is still jiggly, about 1 1/2 hours. Turn the oven off, crack the door open slightly and leave the cheesecake in the oven for 30 to 45 more minutes. Transfer to a rack, run a thin knife around the edge and let cool completely. Cover the cheesecake and refrigerate until fully chilled, at least 8 hours or overnight.
Let the cheesecake sit at room temperature about 30 minutes before serving. Remove the springform ring. Top with whipped cream.