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If you’re following me on Facebook, you may have seen my “To-Do List.” I’m super behind, but I did get a request to post about key lime pie. It’s taken me a hot minute to get to this recipe. But as we enter August in the height of summer, I felt like it was a good time to put key lime tart on the menu.

Making Key Lime Pie as a Tart

First things first, I’ve been itching to make a really pretty tart for ages. While I still haven’t tried a pâte sucrée, I know I can rock a graham cracker crust. So, instead of dusting off my pan for a lemon custard tart, she is making her debut with a key lime tart.

You can, of course, use this same recipe in a pie pan. Give it an extra 5 minutes in the oven, though (20-25 minutes).

Because the bottom of the tart pan is loose, I recommend setting it on a sheet pan just to avoid the super embarrassing “pop-up.” I hope I’m not the only one who has accidentally pushed too hard on the bottom and popped a tart out before it was ready and ended up with a giant mess on the floor.

My Favorite Graham Cracker Crust

The secret to my key lime tart is the graham cracker crust. Adding a little extra depth of flavor is the undertone of browned butter. Spending the extra 5 to 10 minutes browning the butter. It adds a little “Wow! What is that flavor?” to an already awesome pie.

I like to use a little powdered sugar and a pinch of salt, too. Yes, it’s fine to skip these, but here’s what you’ll miss out on. The beauty of salt is it pumps up your flavors. You just need a little here.

But the powdered sugar helps the butter to bind to the graham crackers. This means your crust will hold its shape a little bit better.

Finally, you want to give it a bake in the oven to set its shape. I go for a slightly hotter oven that I’m baking the end product to evaporate any unwanted liquid in the butter and to really add that layer of toasty flavor. Cool it completely before you add in the filling.

Making Key Lime Pie Filling for a Tart

The filling of a key lime pie, and a key lime tart in this case, is like a custard. We’re simplifying by using sweetened condensed milk, but it turns out perfect. So, you’ll start with your limes, right?

Key Limes vs. Limes

You can use regular, Persian limes in your key lime pie filling if that’s what you can find. Really, that is okay. The main difference is that key limes are a little more tart, a little more fragrant (and they have more seeds), and they are smaller.

So, you’ll want to get a bag of key limes and give them a little wash. Zest about 5 of them, or more, until you get 2 tablespoons of zest. Most recipes are going to call for 1 tablespoon or less. I like more because it really brings that floral, fragrant note to the front.

Then, you’re going to juice key limes until you have 1/2 cup. You can use bottled juice, but since you need the zest anyway, don’t waste money. Plus, after my sister painstakingly juiced teeny tiny key limes for an hour on our first ever key lime pies, she’d kill me if I said you could take a short cut.

Key Lime Pie Filling

So, to really get into the pie filling recipe, you’ll start with 4 room temperature eggs. Separate out the yolks and set the whites aside. You can hold on to those to make macarons later. Whisk the yolks with the zest until the color lightens and the texture is very thick and ribbony. This will take about 5 minutes.

Then, stream in the sweetened condensed milk as you continue to whisk until combined. This will take about 2 minutes. And then, you’ll whisk in the lime juice until combined, and beat it until it thickens again (another 5-ish minutes).

A slice of key lime tart served from the whole tart

Cover the filling and let it sit on the counter for about 15 minutes. Give it a couple folds with a spatula to release the air bubbles and make sure it’s really thick. It should feel like pudding now.

You’ll spread that into your prepared graham cracker crust, and slide it into the oven for about 15 minutes at 325ºF. After this, slide the tart pan off the sheet pan onto a wire rack and let it cool completely. Once it’s room temperature, move it to the fridge for 4 hours to get nice and chilly.

Super Nice Whipped Cream to Decorate

There are a couple keys to making your whipped cream extra nice to top your key lime tart off the right way. But rest easy! These little extra steps won’t take you any more time than usual.

Don’t over whip the cream! You want to stop when the streaks left by the whisk or beaters look firm. If you keep going, it’ll get chunky and oily. This is because you’re on the way to making butter.
Add a half teaspoon of vanilla per 1/2 cup of cream. This adds just enough fragrance to make it lovely, but not enough that it overpowers everything else.
Use powdered sugar. You can use granulated but you risk gritty whipped cream. Powdered sugar dissolves more readily into the cream, and the added starch helps your whipped cream stabilize so it doesn’t go soupy all over your leftovers.

The Final Touches

First things first! Since you’ve just made your vanilla whipped cream, use a piping bag with an open star tip. You can make your key lime pie look extra nice by piping your whipped cream on in pretty swoops and swirls.

Slice up an extra lime and place half of a lime slice in every other swish of whipped cream. This is a good way to designate serving sizes, too – one lime per slice.

Now, to get your key lime tart out of the pan, center it over a can of beans (or whatever), and gently set it down. Hold the ring of the pan, and slowly and gently ease it off your tart. It should come off easily.

Tools You’ll Need

Here are the tools I use to make my key lime tart with brown butter graham cracker crust.

11-inch Tart pan
Food processor (I use the attachment for my Ninja blender)
Small pan for browning butter
Zester
Hand mixer
Piping bag
Open star tip

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Comment below if you have questions, concerns, or opinions. And tag me @ellejayathome on Instagram or Twitter if you share pictures from any of my recipes. I love to hear from you!