Some days call for a dessert that feels a little fancy but comes together without any fuss. This Key Lime Sheet Cake is exactly that kind of magic bright, citrusy, and so good it disappears before it even fully cools.

There’s something deeply satisfying about a cake baked in a sheet pan. It feeds a crowd, slices beautifully, and travels like a dream to potlucks, cookouts, or lazy Sunday dinners at home.

And this is where everything changes the warm frosting poured right over the cake creates the most dreamy, melty glaze that soaks into every bite.

Table of Contents

Ingredients for Key Lime Sheet Cake

For the Cake:

1 3/4 cups granulated sugar
2 cups all-purpose flour
1/4 teaspoon salt
1/2 teaspoon baking soda
1/2 cup salted butter, melted
1/2 cup vegetable oil
3 fresh limes — zest of all 3 and 1/4 cup fresh lime juice
3/4 cup boiling water
2 large eggs, beaten
1/2 cup buttermilk
1 teaspoon vanilla extract

For the Frosting:

1/2 cup salted butter, melted
4 cups powdered sugar
3 tablespoons whole milk
1 teaspoon vanilla extract
1–2 tablespoons lime juice
Lime zest for garnish

How to Make Key Lime Sheet Cake

Step 1: Preheat and Prep Your Pan

Preheat your oven to 400°F. Generously spray an 11×17-inch rimmed baking sheet with non-stick cooking spray. This size pan is key for getting that perfectly thin, tender crumb.

Step 2: Mix the Dry Ingredients

In a large mixing bowl, whisk together the granulated sugar, all-purpose flour, baking soda, and salt. Getting these evenly combined before adding the wet ingredients ensures a smooth, lump-free batter.

Step 3: Add the Buttery Lime Base

Whisk in the melted butter, vegetable oil, lime zest, fresh lime juice, and boiling water. The boiling water loosens everything up and gives the cake an incredibly moist texture from the very first stir.

Step 4: Finish the Batter

Add the beaten eggs, buttermilk, and vanilla extract. Whisk just until the batter is smooth don’t overmix here. A light hand keeps the cake soft and tender all the way through.

Step 5: Bake to Perfection

Pour the batter into your prepared pan and bake for 11 to 13 minutes. The top should spring back when lightly touched, or a toothpick inserted in the center should come out with just a few moist crumbs. Watch closely this cake bakes fast!

Step 6: Make and Pour the Frosting

While the cake is still warm, whisk together melted butter, powdered sugar, whole milk, vanilla, and lime juice in a medium bowl. Stir until silky smooth, adding a splash more lime juice if needed to thin it out. Pour and spread the frosting over the warm cake so it melts right in. Finish with extra lime zest and fresh lime slices for that gorgeous, sun-kissed look.

Tips for Key Lime Sheet Cake

Use Fresh Limes Only

Bottled lime juice won’t give you that bright, punchy citrus flavor. Fresh limes both the juice and zest are what make this cake taste truly special.

Don’t Overbake

This cake bakes at a high temperature for a short time. Start checking at 11 minutes. Overbaking will dry it out, and you want every slice to stay perfectly moist.

Frost It While Warm

The magic of this frosting is in the timing. Spreading it over a warm cake lets it melt slightly into the surface, creating a glaze-like layer that’s absolutely irresistible.

Customize the Frosting Thickness

If you love a thicker frosting layer, reduce the milk by one tablespoon. For a thinner glaze that soaks in more, add an extra splash of lime juice until it pours like a dream.

Make It Ahead

This cake stores beautifully at room temperature covered for up to two days, or refrigerated for up to four. It actually tastes even better the next day once all those flavors settle in.

Garnish for the Wow Factor

A generous sprinkle of lime zest and a few thin lime slices on top make this cake look bakery-level stunning. It’s a simple touch that makes a huge visual difference especially for photos!

Why You’ll Love Key Lime Sheet Cake

✅ Ready in under 30 minutes from start to finish
✅ Feeds a crowd with minimal effort
✅ Bright, tangy flavor that feels refreshing and unique
✅ No layering, no stacking just pour, bake, and frost
✅ Perfect for summer parties, potlucks, or weeknight treats
✅ Stays moist and delicious for days

Final Thoughts on Key Lime Sheet Cake

This Key Lime Sheet Cake has earned a permanent spot in my recipe rotation, and I know it will in yours too. It’s the kind of dessert that looks impressive, tastes extraordinary, and secretly requires almost no effort at all.

Whether you’re bringing it to a summer gathering or just treating your family on a Tuesday night, this cake delivers that burst of citrusy joy that makes everything feel a little brighter.

Give it a try, save it for later, and don’t be surprised when your guests ask for the recipe before the pan is even empty.

Key Lime Sheet Cake That’ll Make Everyone Beg for the Recipe