Vegan Key Lime Buttercream Frosting

Elevate your vegan desserts with this delightful twist on traditional buttercream. This dreamy vegan key lime buttercream frosting adds a vibrant, tangy zest to cupcakes, cakes, and cookies, making it a must-have for dairy-free diets. Made with just 3 simple plant-based ingredients, this quick recipe is about to become your new favourite topping.

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Dollops of key lime buttercream being piped on a large cookie cake.

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Why I Made This Recipe

A few years ago our family visited the Florida Keys on a cruise and instantly fell in love with the unique flavour of key limes. Their flavour profile is like nothing I’d tried before and is a great combination of tartness with a distinct floral aroma and less acidity than regular limes. I couldn’t resist trying them in a buttercream frosting and the result was incredible – a creamy, zesty frosting that simply enhances any dessert.

The Key West Key Lime Shoppe - photo taken on January 8 2014. A visit to this store inspired my key lime buttercream frosting recipe.

Why You’ll Love this Frosting

This melt-in-your-mouth frosting recipe is not only bursting with flavour but also quick and simple to make, using just a handful of everyday ingredients. If you are looking for something a bit different to traditional vanilla buttercream, this flavour will wake up your tastebuds. And because it’s dairy-free and vegan, it pairs beautifully with allergy-friendly baking.

Ingredients and Substitutions

This vegan key lime buttercream recipe is simple, uses 5 pantry ingredients, and it’s allergen-friendly – nut free, soy free, egg free and gluten free. Here’s what you’ll need, along with my tips and additional FAQs for the best results.

Ingredients to make key lime buttercream, includes icing sugar, butter, salt, vanilla bean paste and key lime juice.

Vegan Butter: I use plant based unsalted butter for a creamy texture. Block-based butter has better results than tub butter due to the lower water content in block butter. If you’re not dairy-free, substitute with regular unsalted butter.

Icing Sugar: Sift your icing sugar if it is clumpy. This ensures a smooth, silky frosting.

Salt: Balances the sweetness. If you are using salted butter, omit the salt.

Vanilla: I prefer vanilla bean paste for rich flavour but vanilla extract works too.

Key Lime Juice: The star ingredient. Fresh key lime juice gives a bright, tangy flavour. If you can’t find key limes or key lime juice, use regular lime juice.

Top Tip: retain the lime zest to add on to the frosting once piped.

How to Make Key Lime Frosting

Making this buttercream is quick and easy. Follow these steps for a smooth frosting that is bursting with flavour.

Prep your ingredients: ensure your butter is at room temperature and your icing sugar is sifted. I recommend using a stand mixer to make the frosting but a hand mixer will also work well.

In a stand mixer, beat plant-based butter until soft and fluffy. This step is key to lighten the frosting and add airiness.

Gradually add in the icing sugar and salt, pulsing a few times at first to prevent a big cloud of icing sugar going everywhere. ) and then continue to mix until fully incorporated.

Icing sugar and salt being mixed in with butter in a stand mixer bowl.

Add in the vanilla bean paste and key lime juice and mix until silky smooth.

Adding vanilla bean paste to buttercream in a stand mixer bowl.

Top Tip: add the key lime juice as the buttercream is mixing. This helps to incorporate it quickly.

Adding key lime juice to buttercream in a stand mixer bowl.

The buttercream frosting should have a soft, spreadable consistency. If I close my eyes while I eat some, I can imagine myself back in the Florida Keys.

Close up of key lime buttercream in a stand mixer bowl.

Your frosting is now ready to spread or pipe onto cupcakes, layer cakes, cookies, or even a cookie cake. The texture is silky, soft, and perfectly tangy – like a little taste of the Florida Keys in every bite!

Serving Suggestions

This vegan key lime buttercream frosting is very versatile and pairs well with a variety of desserts. Here’s a few of our favourite ways to enjoy it:

Vanilla Cupcakes – pipe a generous swirl on your favourite cupcakes for a tangy topping.
Vanilla Layer Cake – use as a filling between layers or all over the cake for a zesty twist.
Sugar Cookies – spread on top or create a fun, tangy cookie sandwich.
Cookie Cake – perfect for Mother’s Day, birthdays, or any celebration that calls for something different.

Pro Tip: For a striking presentation, add a sprinkle of lime zest or edible flowers on top of the frosting.

Close up of a decorated Mother's Day cookie cake topped with buttercream, biscuits, royal icing flowers, sprinkles and mini marshmallows

Storage and Freezing

This buttercream is easy to store and keeps its creamy texture, making it perfect for prepping desserts ahead of time.

Storage: Store leftover buttercream frosting in an airtight container in the fridge for 1 week. Before using, allow it to come to room temperature and give it a quick stir for a smooth consistency.

Freezer: This buttercream freezes beautifully for up to 3 months in an airtight container. To use, thaw at room temperature then re-whip before using to restore its fluffy texture.

Common Buttercream Questions

What is the difference between regular limes and key limes?

Key limes are smaller, rounder, and slightly sweeter than regular limes. Their unique flavour is less tart and slightly floral, making them perfect for desserts like frosting and key lime pie. If you can’t find key limes, regular lime juice works just fine.

Can I make this buttercream frosting ahead of time?

Absolutely. You can make this up to a week in advance and store it in the fridge in an airtight container. For longer storage, freeze for up to 3 months and rewhip before using.

How much frosting does this recipe yield?

This recipe makes approximately 3 US cups, enough to ice an 8-inch layer cake, a batch of cupcakes, or a cookie cake.

Can I adjust the lime flavour?

Yes! Add more key lime juice or zest to intensify the tang, or reduce for a milder flavour. Taste as you go to find your perfect balance.

What’s the best way to pipe this frosting?

Use a star or round piping tip for a smooth, fluffy swirl. If the buttercream seems too soft, chill it in the fridge slightly before piping.

Share The Zest

This vegan key lime buttercream frosting will transform any dessert into a bright, tangy treat. Enjoy a little taste of the Florida Keys from the comfort of your kitchen. Let me know in the comments if you try this recipe, and don’t forget to tag me on Instagram @itsbakeangel with your creations – I love seeing your homemade treats!