To prepare crust, combine graham cracker crumbs and melted butter in a small bowl. Mix until a moist yet crumbly mixture forms. Firmly press the mixture into the bottom and sides of the prepared pan.
Bake for 10 minutes. Let cool completely on a wire rack.
To prepare filling, combine gelatin, cinnamon, ginger, salt, condensed milk and eggs in a saucepan. Let stand for 10 minutes. Then cook over low heat, whisking continuously, until gelatin dissolves. Remove from heat.
Stir in pumpkin. Mix to combine.
Pour the mixture into the cooled graham cracker crust
Refrigerate the tart(s) until set, at least 3 hours, or preferably overnight.
Before serving, in a large heatproof bowl, combine sugar and egg whites. Using a handheld electric mixer, beat on high speed until foamy for a minute. Set bowl over a pan of barely simmering water. Beat on high speed until stiff peaks form, about 6 minutes.
Remove from heat, stir in water, and beat for another 2 minutes until mixture thickens.
Transfer meringue to a large pastry bag fitted with a wide plain pastry tip and pipe large tips on the tart(s). Using a kitchen torch, lightly brown the meringue.