Line a 9-inch springform pan base with parchment. Set aside.
Stir graham crumbs, brown sugar, and a pinch of salt in a bowl. Pour in melted butter and mix until evenly moistened.
Press the crust mixture firmly into the pan bottom. Chill while you make the filling.
Beat softened cream cheese with powdered sugar until smooth and fluffy, about 2 minutes.
Mix in pumpkin puree, vanilla, pumpkin pie spice, cinnamon, salt, and lemon juice until fully blended.
Whip cold heavy cream to stiff peaks in a separate bowl.
Fold the whipped cream gently into the pumpkin mixture until no streaks remain.
Spread filling over the chilled crust and smooth the top. Cover and refrigerate at least 6 hours or overnight until set.
Release the springform, slice, and serve. Dust with extra cinnamon if desired.