Preheat oven to 325°F.
Grease an 8x3-inch springform pan, then line the bottom with a greased parchment circle.
To make the crust: Pulverize the graham crackers and pecans in a food processor, then add the butter, sugar, and salt and blend until incorporated.
Dump the crust mixture into the prepared pan and press tightly to the bottom and sides. The crust will come up to about 2/3 of the 3-inch-high pan. Bake the crust for about 10 minutes or until golden-brown and toasty.
*Pro tip: if you prefer the crust to only be on the bottom of the cheesecake, reduce the ingredients by half and press just onto the bottom of the pan.
To make the cheesecake: In a stand mixer, beat the cream cheese on medium-low speed with the paddle attachment for about 1 minute. Scrape down the sides and mix for another 30 seconds. Add the sugar and mix for about 1 minute. Scrape down the bowl and mix for another 30 seconds. Add the eggs one at a time, scraping down the sides after each. Add the sweetened condensed milk and mix until combined. Scrape the bowl. Add the key lime juice, vanilla extract, salt, and zest. Mix until uniformly mixed, about 30 seconds.
Pro tip: mixing on medium low speed mixes the cheesecake without incorporating lots of air bubbles, which can make your cheesecake souffle and crack. Cracking cheesecake is not the end of the world but something we try to avoid.
Pour the cheesecake mixture into the crust. Tap the pan very lightly on the counter to bring up any large air bubbles.
Place the cheesecake in the oven on a baking sheet. Place a second baking sheet on the rack beneath the cheesecake and fill it with about a 1/4-inch boiling hot water.
Pro tip: When using an old spring form pan that may leak, I don’t like to use a water bath, but I still want water in the oven to regulate the temperature. The pan of water will help the cheesecake bake evenly and prevent the top from drying out and cracking.
Bake for about 40-50 minutes or until the cheesecake is just puffed and set in the middle.
Pro tip: The timing will be longer if your ingredients are not fully at room temperature. Cheesecake doesn’t mind a long bake, so don’t panic if it still hasn’t set up, just wait for it.
To make the curd: About 30 minutes before the cheesecake is done baking, make the lime curd, so it is still warm when you put it on top of the cake.
Whisk together all the curd ingredients except the butter in a large metal bowl. Place the bowl over a pot of gently simmering water set up as a double boiler. Stir constantly with a rubber spatula until the curd begins to thicken, about 10 minutes. Add the butter and continue to stir until it is completely melted and the curd is quite thick; it will be the consistency of smooth pudding.
Pro Tip: If you are using lime curd you made in advance or got from the store. Heat it gently over the stove or in the microwave for 10 seconds so that it is slightly warmer than room temperature. This will allow it to spread easier and bake in the proper amount of time.
Remove the cake from the oven, strain the lime curd over the top, using as much as needed to reach the top rim, there may be leftovers, which can be covered and left in the refrigerator. Return the cheesecake with curd to the oven and bake for an additional 8 minutes.
Remove from the oven and run a small paring knife blade around the edge of the pan.
Pro tip: Dip the knife in hot water before running it around the pan. The wet heat of the blade will smoothly cut the curd and cheesecake away from the pan without dragging crumbs. Cutting around the cake while it is still hot from the oven separates it from the pan and allows it to shrink freely as it cools, without cracking.
Allow the cheesecake to cool on a wire rack until room temperature, about an hour. Then refrigerate until chilled, another hour. Cover the top once chilled and refrigerate for another 3 hours or overnight.
Pro tip: The initial room temperature cooling is part of the baking process, so don’t rush it or the cheesecake may not be as set as you’d like and it may crack from cooling too fast. Having said that, there is nothing wrong with a VERY soft, Basque-like texture, so if your cake is soft, just tell people you meant it to be that way. ;)
