Add the graham cracker crumbs to a bowl along with the melted butter. Stir well to combine.

Press the crumb mixture into the bottom of an 8-inch tart pan and up the sides of the pan using the back of a spoon or bottom of a measuring cup. Set aside.

Pour the sweetened condensed milk into a bowl and add the juice and zest of the 3 lemons.

Slowly pour in the heavy whipping cream, mixing with a hand mixer (or use your stand mixer fitted with the whisk attachment) while you continue to pour the whipping cream in a steady stream.

Continue mixing on medium-high speed for 2-3 more minutes until the filling becomes slightly thicker and glossy.

Pour the filling into the prepared crust and refrigerate for about 6 hours or overnight.

Slice and serve, topping each slice with a dollop of whipped cream and some lemon zest.