Key Lime Bars with Cinnamon Graham Cracker Crust

When you're lucky enough to find key limes, put them to good use and make these Key Lime Bars! They're an easy-to-make summer treat with the perfect balance of tart and sweet.

(This recipe for Key Lime Bars was originally published in April 2009, but was updated with new photos and content in 2020).

Are you a chocolate or fruity dessert person? Come on; you know there are two types of people in the world! I used to always favor chocolate, but as I get older, I find myself being pulled more to the fruity dessert side of things. I love strawberry shortcake, sherbet, chocolate-covered strawberries, apple pie... just to name a few!

And if I see a key lime dessert on a restaurant menu? I'm automatically in. Key limes just scream summer and happiness to me and I feel like they're ignored far too often.

One of the best ways to enjoy key limes? Key lime bars! This simple recipe from Martha Stewart looked great, so I went forward with it after slightly adapting.

Key Lime Bars Recipe

I'm a huge fan of key limes, though believe it or not, they're actually not that different from conventional limes. Did you know that key limes are actually much more prevalent around the world than the conventional limes we're used to in the U.S.? (I share more key lime history in this post).

But since key limes aren't that prevalent around here and I find the flavor a bit more floral and sweeter than regular limes, I get really excited when I see them at the market.

This recipe for key lime bars puts those buggers to good use and despite it taking a little time to squeeze the juice out of them, this summer dessert is quite easy to make!

I started with the cinnamon graham cracker crust, which is a simple mixture of cinnamon graham crackers, sugar, and melted butter. Once pulsed in a food processor or blender, you'll press the mixture into the bottom of an 8-inch square dish and bake at 350 degrees for 10 minutes.

Then comes the key lime filling mixture. In the bowl of an electric mixer with whisk attachment or in a large bowl with a hand mixer, add egg yolks and lime zest. Mix for about 5 minutes on high speed, until the mixture is nice and thick.

Reduce the speed to medium and add the sweetened condensed milk in a slow stream.

Bring speed back up to high, mix for an additional 3 minutes, until thick. Bring speed to low and add in the fresh squeezed key lime juice and mix until combined.

I almost wanted to put a straw into that bowl. Would that be weird?? Probably.

Pour the filling over the baked graham cracker crust and, using a rubber spatula, spread it evenly. Bake for about 10 minutes until the filling is set.

Let bars cool completely on a wire rack then refrigerate for at least 4 hours or overnight.

Once chilled, slice into 2-inch bars. Top with whipped cream, little key lime wedges, and additional lime zest, if desired.

Why HELLO, love. These key lime bars are tart and smooth and the crunch from the crust makes them the perfect little dessert to cool you down this spring and summer!

Tips and Substitutions

These key lime bars are delicious as is, but I do have a few ideas for substituting ingredients and materials if necessary:

• If you can't find key limes, you can use conventional limes. The flavor may be ever so slightly different, but most people report no big taste difference between key limes and conventional limes, so chances are nobody will know. You can even still call them key lime bars! Shhh.
• I recommend fresh squeezed key lime juice, but I won't tell anyone if you buy a little bottle of key lime juice instead!
• Zesting key limes can be a major pain, so feel free to zest conventional limes instead.
• If you don't have a mixer or blender, you can crush the graham crackers in a bag (I like putting the bag on a cutting board and using my meat mallet) and then mix the graham cracker crumbs with the sugar and melted butter in a large bowl.
• If you can't find cinnamon graham crackers, plain graham crackers work fine, too. You can add a bit of ground cinnamon in, if you like, but it's not totally necessary.
• I recommend topping with whipped cream right before serving as it tends to get liquid-y after sitting for too long (especially if you're using homemade)

At first I was worried these were a bit too tart. But by the time I took my second bite, I realized they they truly are the perfect balance of tart and sweet. There's no actual granulated sugar in the key lime bars, but the sweetened condensed milk introduces both sweetness and creaminess to the filling.

I like the way the cinnamon graham crackers add a little kick to the tartness, but like I mentioned above, they'd be delicious with a plain graham cracker, too.

If you love key limes as much as I do, be sure to check out my Key Lime Pie Mojitos and my Key Lime Pie Popcorn. And I can't wait to try this Key Lime Frozen Yogurt from A Zest for Life!

Do you have a favorite key lime dessert?