5 from 22 votes

Key Lime Pie Bars

Name: Key Lime Bars
Prep time: 15 min
Cook time: 15 min
Total time: 30 min
Ingredients: 1 ½ cups graham cracker crumbs; 2 Tablespoons sugar; 1 Tablespoon brown sugar (firmly packed); 6 Tablespoons butter (melted); 2 14 oz cans sweetened condensed milk; ⅓ cup sour cream; 2 teaspoons lime zest (optional); ⅔ cup key lime juice; homemade whipped cream (for topping, optional. Click the link for the recipe, you will only need 1/2 batch. )

By Sam MerrittPublished Aug 01, 2021

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56 Comments

Servings: 16 squares

30 mins

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Key Lime Pie Bars are a little sweet, very tart, and smooth and creamy over a crumbly golden (homemade) graham cracker crust. They’re also incidentally egg-free! Can you believe these take only minutes to prep and bake? Recipe includes a how-to video!

square of creamy key lime pie bar on marble, topped with whipped cream and lime zest

Rich, creamy, and only slightly sweetened, these key lime pie bars are perfectly tart, enough to make your mouth pucker just thinking about them. Fans of my lemon bars will love these tart treats (and perhaps even more they’ll love how easy these bars are to make in comparison).

Served on a crumbly, perfectly sweetened graham cracker crust, today’s recipe is obviously inspired by my key lime pie, but look closely at the ingredients (which I highlight below) and you’ll see that there are some noteworthy differences.

What You Need

Sweetened Condensed Milk. This is the base of our pie filling and serves as our sweetener. Do not substitute evaporated milk (this seems to be a common mistake, please note they are not the same thing and your bars will not only taste right but they won’t set properly if you use evaporated milk).
Sour cream. To make this recipe easy (and, incidentally, egg free), I ultimately ended up swapping out the the 6 egg yolks that I used in my pie recipe with sour cream (I can’t help wanting to change things up from recipe to recipe!). The results are rich and creamy and a bit more tart/sour than my classic pie, but every bit as good!
Key limes. Key limes are tiny (ping-pong-ball-sized) limes that may be either green or yellow (or a spotty combo of the two colors) that have a flavor that’s distinct from their more common grocery store counterparts (which are typically Persian limes). While I recommend using fresh key limes if you can find them, unfortunately I have always had a lot of trouble finding these in any grocery stores within 20 miles of me. If you can’t find key limes, don’t use “regular” limes, instead find yourself a bottle of key lime juice! Nellie & Joe’s brand is what I use, it’s typically sold near the lemon juice and I included a photo above.

SAM’S TIP: Here’s a hand-saving tip if you’re able to find fresh key limes: Use a garlic press!. Halve your limes, place them in the press (rind-side up) and then squeeze the juices into a measuring cup. So much easier than hand-squeezing!

Then of course you’ll also need graham cracker crumbs, sugar, and butter to make your graham cracker crust. Salted or unsalted butter will work equally well in the crust. I like to use a Tablespoon of brown sugar to help enhance the flavor of the crust, but if you don’t have any you can use all granulated sugar.

While it’s not strictly necessary, I highly recommend topping your bars with dollops of homemade whipped cream before serving. It adds a light, sweet, contrast to the otherwise tart bars!

How to Make Key Lime Pie Bars

Prepare the graham cracker crust! Stir together graham cracker crumbs, sugar, and melted butter. Stir until all of the crumbs are coated with butter and the mixture is sandy and well-combined.
Press crumbs into the bottom and part-way up the sides of a foil-lined 9×9″ baking pan. Press the bottom into an even layer, I like to use the back of a spoon or the clean, flat bottom of a measuring cup to do this.
Whisk together the remaining ingredients (I actually recommend whisking together all of the ingredients except for the key lime juice, then whisking that in last as it’s much thinner than the other ingredients and adding it with the other ingredients can make it harder to incorporate) until the mixture is smooth.
Pour key lime pie bar batter into prepared pan and use a spatula to spread the filling so you have a smooth layer.

SAM’S TIP: Lining the pan with foil isn’t absolutely necessary, but it does make it much easier to remove the key lime pie bars from the pan after baking. Make sure you use a long enough piece of foil that it hangs over two of the sides of the pan (creating a sort of sling). After baking and completely cooling the bars, use the excess foil to carefully lift them out of the pan, then easily cut and serve on your counter.

Frequently Asked Questions

Can I substitute a different lime if I can’t find key limes?

I do not recommend it, as most limes available in the grocery store are Persian limes, which have a distinctly different flavor. If you can’t find key limes, purchase key lime juice instead, which can often be found near the lemon juice.

Are key lime pie bars supposed to be green?

No! Green key lime pie is usually that color due to added food coloring. Key lime pie should be a creamy white/yellow color.

Can I make this as a pie?

I don’t see why not! If you have excess batter, simply discard it, do not overflow your pie plate. I also should note that I already have a killer key lime pie recipe on the blog and prefer that when making a pie.

Enjoy!

Let’s bake together! I’ll be walking you through all the steps in my written recipe and video below! If you try this recipe, be sure to tag me on Instagram, and you can also find me on YouTube and Facebook

5 from 22 votes

Key Lime Bars

Key Lime Pie Bars are a little sweet, very tart, and smooth and creamy over a crumbly golden (homemade) graham cracker crust. They're also incidentally egg-free! Can you believe these take only minutes to prep and bake? Be sure to check out the how-to video!

Prep: 15

Cook: 15

Total: 30

Servings: squares

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Equipment

Ingredients

Graham Cracker Crust

▢ 1 ½ cups (170 g) graham cracker crumbs
▢ 2 Tablespoons sugar
▢ 1 Tablespoon brown sugar, firmly packed
▢ 6 Tablespoons (85 g) butter, melted

Key Lime Pie Bar Filling

▢ 2 14 oz cans (795 g) sweetened condensed milk
▢ ⅓ cup (75 g) sour cream
▢ 2 teaspoons lime zest, optional
▢ ⅔ cup (150 ml) key lime juice
▢ homemade whipped cream, for topping, optional. Click the link for the recipe, you will only need 1/2 batch.

Instructions

Graham Cracker Crust

Preheat oven to 350F (175C) and line a 9×9" (23x23cm) baking pan with foil. Set aside.
Combine graham cracker crumbs, sugar, and brown sugar in a large bowl.
1 ½ cups (170 g) graham cracker crumbs, 2 Tablespoons sugar, 1 Tablespoon brown sugar
Add melted butter and stir well.
6 Tablespoons (85 g) butter
Press evenly and firmly into the bottom and up the sides of prepared pan.
Bake on 350F (175C) for 7-8 minutes. Allow to cool slightly while you prepare your key lime filling.

Key Lime Filling

In a large bowl, whisk together sweetened condensed milk, sour cream, and lime zest (if using) until mixture is smooth.
2 14 oz cans (795 g) sweetened condensed milk, ⅓ cup (75 g) sour cream, 2 teaspoons lime zest
Gradually whisk in key lime juice until mixture is smooth.
⅔ cup (150 ml) key lime juice
Pour into prepared pie crust and bake for 8-10 minutes, until mixture is set if you jiggle the pan.
Remove from oven and allow to cool to room temperature, then transfer to refrigerator and allow to chill 4-6 hours before cutting.
Top with whipped cream, if desired, and serve.
homemade whipped cream