For the Crust:

1. Prepare the Crust: In a medium bowl, combine the graham cracker crumbs, melted butter, and erythritol. Mix until the crumbs are evenly coated with the butter and the mixture resembles wet sand.

2. Press into a Pan: Press the mixture into the bottom of a 9-inch pie pan, making sure to evenly distribute it along the bottom and up the sides.

3. Chill: Place the crust in the refrigerator to chill while you prepare the filling, at least 30 minutes.

For the Lemon Filling:

1. Prepare the Gelatin (optional): If using gelatin for a firmer texture, dissolve the gelatin in 2 tablespoons of warm water. Let it sit for a few minutes to bloom, then gently heat it until completely dissolved (in the microwave or on the stovetop). Let it cool slightly before using.

2. Make the Filling: In a large mixing bowl, beat the softened cream cheese until smooth. Add the powdered erythritol, lemon juice, lemon zest, and vanilla extract. Continue mixing until smooth and creamy.

3. Whip the Cream: In a separate bowl, whip the heavy cream until stiff peaks form.

4. Combine: Gently fold the whipped cream into the cream cheese mixture until fully combined. If you’re using gelatin, fold it into the mixture now.

5. Fill the Crust: Pour the lemon filling into the chilled graham cracker crust, smoothing it into an even layer.

6. Chill: Refrigerate the pie for at least 4 hours or overnight to allow it to firm up.

Serve:

1. Garnish (optional): Garnish the pie with fresh lemon slices or whipped cream before serving.

2. Slice and Enjoy: Once set, slice and enjoy this light, refreshing, and sugar-free lemon pie!