Place them in a large bowl, add melted butter and mix well to combine.
Divide mixture among four tart pans with removable bottoms, and press evenly on bottoms and up sides. Refrigerate until firm, at least 15 minutes.
In a saucepan, combine cream and sugar, cook on medium heat for about 5 minutes, stirring from time to time and then remove from heat.
Add lemon zest and juice, mix well and let cool for 20 minutes.
Divide among crust-lined tart shells and refrigerate until set, at least 4 hours.
In a heatproof bowl, combine the egg whites, sugar, cream of tartar and vanilla.
Bring a saucepan with a few cm of water to a simmer. Set the bowl over the simmering water, making sure the water does not touch the bottom of the bowl.
Stir continuously the mixture until the sugar has dissolved around 5 minutes and the egg whites are very warm to the touch.
Remove bowl from heat, then beat the meringue on medium-low speed until foamy around 2 minutes, then increase the speed and beat until getting a stiff peak around 4 minutes. Beat in vanilla.
Spoon over tarts, then use a torch to lightly toast.
Notes
Prep Work: Ensure all your ingredients are at room temperature before you begin. Chill the Crust: After pressing the crust into the tart pan, chill it in the refrigerator for at least 30 minutes. This helps the crust set properly and prevents it from crumbling when you add the filling.Strain the Lemon Juice: To ensure a smooth and silky filling, strain the lemon juice before adding it to the other filling ingredients. This will remove any pulp or seeds that may affect the texture.Gradually Add Sugar to the Meringue: Gradually add sugar to the egg whites while still beating them. This makes the meringue stable and gives it a fluffy, light texture.Use Cream of Tartar: By adding a bit of cream of tartar to the egg whites, you can make them more stable, helping the meringue keep its shape. This gives you a fluffier and steadier topping.Storage: Store the leftover lemon pies in an airtight container or cover them tightly with plastic wrap in the refrigerator.