Key Lime Frosting Recipe

I absolutely love any citrus desserts for Easter or spring. And key lime is no exception. So I figured I would make this delicious Key Lime Frosting Recipe that is perfect to go on top of key lime bars. Or even key lime cupcakes. 

All you need is some key lime zest, powdered sugar, fresh key lime juice, all purpose flour, and butter to make this delicious frosting recipe! And you don’t have to make this frosting recipe for the bars like I did. You could easily make this frosting for a key lime cake or key lime pie cupcakes too. 

Whatever dessert you make, this recipe is guaranteed to be a big hit! It is packed with a great key lime flavor that is delicious without being over the top! Keep on reading for the full recipe instructions on how to make it! 

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Ingredients Needed for Key Lime Frosting

For the purpose of this recipe, I will be making key lime bars to accompany the frosting with. But, like I said above, feel free to use this frosting recipe for any delicious key lime dessert you have in mind!

This recipe makes more of a key lime buttercream frosting seeing as how you use softened butter and not cream cheese for a key lime cream cheese frosting recipe. 

For the crust: 

• 1¾ cups all purpose flour
• ¾ cup butter softened
• 1/4 cup sugar
• 1/2 cup chopped pecans

For the filling:

• 1 ½ cups sugar
• 4 eggs
• 4 Tbsp flour
• 4-5 Tbsp fresh key lime juice
• ½ tsp baking powder

For the key lime frosting:

• 2¼ cups confectioners’ sugar
• 1½ Tbsp butter softened
• 2-3 Tbsp fresh key lime juice
• Freshly grated key lime peel

How to Make Key Lime Bars With Frosting

Start by preheating oven to 350 degrees. Grease a 9×13 baking pan. Then, with an electric mixer, combine all the ingredients for the crust using a paddle attachment, minus the pecans. Beat at a low speed in a large bowl until everything is combined and looks coarse crumbs. Add in the pecans to the flour mixture.

Press the mixture evenly down into the prepared baking pan. Bake in preheated oven for 15-20 minutes. Mine took about 18 minutes total. You want it to be a nice golden brown color, but not over bake it.

While the crust is baking, make the filling mixture. Combine all the ingredients for the filling listed above at a medium speed in the bowl of a stand mixer. Be sure to scrape down the sides of the bowl as you go too.

The amount of lime juice depends on your preferences, but I definitely used the full 5 tablespoons for the filling. I love the taste of fresh key limes compared to bottled key lime juice. Trust me, it’s worth it to juice your own!

Also, regular limes are not the same thing as key limes. They are more of a small lime, so it does take more to juice them, but they are delicious! Even though you can use fresh lime juice in a pinch, I highly recommend trying to find key limes if available to you!

After crust has partially baked, pour prepared filling on top. Bake in oven again for another 18-20 minutes. Let the bars cool completely to room temperature before frosting. 

How to Make Key Lime Frosting 

Now that you’ve made the bars and they are completely cooled, you can now make the key lime frosting! Which is the best way to enjoy all the key lime flavor in my opinion! Simply, mix all the ingredients listed above at a medium-high speed in your stand mixer until fully combined.

Then, pour frosting on top of cooled key lime bars and spread evenly across. You don’t need a piping bag for this frosting as it is not thick and spread easily. You could even add in more of a green color using green food coloring if you are making this for St Patrick’s day too! That would look perfect on some bundt cakes too! 

After you have frosted the bars, apply the key lime peel evenly on top. To make this process faster, I grated the key limes while everything was in the oven baking.

Then, I stored the peel in the fridge covered in plastic wrap. I just brought it out when I needed it, and then I was done! Easy peasy! You could also garnish each individual bar with some key lime slices if you prefer too! 

Enjoy Your Key Lime Frosting Bars!

I hope you enjoyed this easy and delicious recipe! As you can see the baking time and the prep time to this recipe is minimal and very simple!

This is the perfect Easter or springtime dessert to enjoy with your friends and family! If you make it, let me know how it goes for you! I am sure you will love it too.

And the next time you’re in the mood for another key lime dessert idea, be sure to check out my key lime pie recipe too!