While the pie dough is cooling down, prepare the marshmallow.
Pour the gelatin into a container with the water and let it hydrate for at least 5 minutes.
In a saucepan, pour half of the maple syrup and heat it until it starts to smoke. Then, add the rest of the syrup and the glucose, stirring it to well dissolve. Let it simmer for about 1 minute.
Remove it from heat and pour it into a container. Add the gelatin and stir until they are well incorporated. Add the lemon zest.
Whisk during 10 to 15 minutes. The mixture will swell and change its texture and color. You will get into the right consistency when the mixture forms stiff peaks.
Then, pour the marshmallow into the pie crust. Keep aside the marshmallow into the crust for about 30 minutes, so it sets down.