Break graham crackers into pieces.

Dice butter.

Pulse graham crackers and butter in a food processor until the mixture resembles brown sugar.

Press the mixture onto the bottom of a 9-inch springform pan to form the crust.

Chill the crust in the refrigerator.

Mix condensed milk and gelatin in a small pan.

Heat over very low heat until the mixture just starts to boil (about 2 minutes).

Combine cream cheese and lemon zest in a mixer bowl.

Beat on medium-high speed until the mixture is smooth (about 2 minutes).

Add the condensed milk mixture to the cream cheese mixture and mix until blended.

Using a spatula, lightly mix in half of the dulce de leche, creating a marbleized look.

Gently pour the cheesecake mixture into the pan, smoothing it into an even layer.

Chill covered for at least two hours, preferably overnight.

Cover the cheesecake with the remaining dulce de leche.

Serve chilled.