Place ¼ cup water in a small bowl and sprinkle gelatin over top of the water. Set aside to allow it to bloom.
Whisk the egg yolks, sugar, lemon juice, zest, and salt in a medium bowl and set over a medium pot of simmering water. (You only need a couple of inches of water in the pot. Do not allow the bottom of the bowl to touch the water.) Cook, stirring occasionally until the mixture has thickened slightly, approximately 18 minutes.
Remove from the heat and whisk in the gelatin mixture until thoroughly combined. Cool completely at room temperature, or refrigerate for 25-30 minutes, stirring frequently.
Beat egg whites on medium-high speed until stiff peaks form, 1-2 minutes. (Being careful not to break the whites) Fold the whites into the cooled yolk mixture using a spatula or a spoon with a whole in the middle, so as to keep as much loft in the mixture as possible.
Pour the chiffon into the baked pie shell and refrigerate for at least 4 hours, or overnight.
Serve with slightly sweetened whipped cream and fresh raspberries