Key limes are smaller in size than your standard Persian limes you get year-round at the grocery store. They’re much more tangy and acidic, but are only in season from May to September. This is the opposite of most citrus fruits, which are actually in season during the winter months. They’re more sour than regular limes, and that’s what makes them so darn special.
The only drawback to these little guys is their small statue makes juicing them take a liiiiiiiitle bit longer. How do I know?
Trust me. I know.
But to be honest, I didn’t mind it because I know the best available ingredients produce the best tasting results. Every. Time. It’s nice to have it pre-juiced but the zest is so flavorful that you can’t replicate that in a bottle. Also, remember to zest before you juice. It sounds stupid to say, but it’s so easy to forget and most of us have done it at least once.
When doing my research prior to writing this article and developing the recipe, (Yes I do that and yes you’re welcome all 3 of you food nerds like me out there) I read several articles, some devoutly swearing the difference in taste between key limes and Persian limes another discussing historical terroir of Floridian and Central American soil versus that of the 1920s. Both sides made valid arguments and I decided that sine I cannot go back in time to neither farm limes nor hoard them all for the future, I decided to go with my own completely wild and highly unscientific method.
I just freaking ate them. <GASP!>
Well, to clarify I basically tried straight shots of the juice from both key limes and standard Persian limes. Taste is the best culinary test there is, right? And I concluded this: they DEFINITELY taste different. The Persian or standard limes were light and floral, not just bitterly tart. But the key limes were entirely a different breed, they were tangy and acidic. They are unique and perfect in their own right- as long as you properly source where the key limes are from. As long as it says they’re from Florida somewhere on the bag- you’re good to go. They are undoubtedly MUCH more tart than Persian limes… like, mouth-puckering, jumping-around-my-kitchen, making-weird-clicking-sounds-with-my-mouth T-A-R-T. And then it hit me: this is exactly what you want, if you think about it. You’re combining the super-sour juice into a creamy custard-like pie and using dairy (which is usually sweetened condensed milk) to offset the extreme acidity. That’s why key limes work so well here- and that’s the only reason they works so well here. Another example is key lime pie cheesecake, or key lime ice cream. Go onto Pinterest and type in “Key Lime Recipes” and I guarantee you 90% of them have dairy incorporated in some way. Because you have to.
In any other sort of combination where you’d use a traditional lime in a recipe and you substitute out a key lime, is going to taste awful and astringent. Richness and cream cut through the acid in a recipe-any recipe. It’s the balance of sweet, bitter/sour and fat that make a dish really perfect. Sweet (sugar in crust), Salty (macadamia nuts), Sour (key limes), and fat (dairy/sweetened condensed milk). The other rule to heed is avoid Mexican key limes at all costs. They’re tiny so they yield almost no juice, are extremely bitter and very expensive. They were bred to replace the Floridian key limes but they’re growing conditions did not respond well. I know this from research, not taste since I couldn’t find any around me. Which sounds like it’s a very good thing.
So in the end, I guess both sides of the great lime debate won- they just need the proper context. Yes, as long as you get the Florida variety in season- they do taste quite different. Standard Persian limes can absolutely be substituted for key limes in a recipe. But key limes are NOT a substitution for pretty much anything else you’d use a lime for.
So do you really need to use KEY limes for this pie recipe?
Of course not.
But will it taste the same if I use regular limes?
Of course not.
Should I shy away from this pie if I can’t find key limes?
Of course not.
This is the consistency you want your crust to be before making it. And make sure to look as homeless as possible when planting your new tart pan on your old
This pie is absolutely divine regardless of which one you use and the crust is out-of-this-world. It’s so easy and if you’re REALLY that worried about it I would juice one or two Meyer lemons if you have them and add them to the regular lime juice. They’re more floral than regular limes and will be the closest in flavor. Have fun making this pie and use whatever limes you can get your hands on, it will be delicious either way- I promise.
I’d just avoid doing shots of the juice if I were you- pretty sure parts of my taste buds will never ever forgive me.
Key Lime Tart with Macadamia Nut Crust
Makes one 9 inch tart
1 sleeve/about 9 Honey Graham Crackers
1/2 C. Toasted macadamia nuts (Save a few for garnish, if desired)
2 tbsp brown sugar
¼ tsp kosher salt
5 tbsp melted butter
3 large egg yolks
1-14 oz can sweetened condensed milk
1 tsp lime zest
2/3 C. Key lime juice (approx a 1 lb bag of key limes, can supplement additional with standard lime juice)
1 C. Whipped cream
Hazelnuts/Lime Slices/Zest to garnish
A 9-inch removable-bottom tart pan
A zester (I love the Microplane brand)
Preheat oven to 350 degrees and spray a 9-inch tart pan with non-stick spray. Set aside on a baking sheet.
In the bowl of a food processor, put in the graham crackers, macadamia nuts, brown sugar, and salt and pulse until the mixture looks like sand.
With the processor on low, slowly pour in the melted butter through the open spout on lid and process until mixture resembles wet sand and can stand up when pushed against the side of the bowl (See picture above)
Pour graham cracker mixture into the tart pan and evenly spread it on the bottom and up the sides. Bake for 10 minutes and remove from oven to allow to cool. Leave the oven on, howev .
In a large bowl, whisk together the 3 egg yolks
Add in the sweetened condensed milk, lime juice and zest and combine until filling is smooth
Pour filling into the slightly cooled crust and bake for 18-20 minutes or until the center is only slightly jiggly
Remove from oven and allow to cool completely. Cover and refrigerate for at least 2 hours, or overnight.
Before serving, dollop the edges with whipped cream and garnish with lime zest, hazelnuts or lime wedges. Enjoy!