Vegan Vanilla Sheet Cake with Mixed Berry Buttercream Frosting (Sugar Free and Gluten Free options)

This eye popping treat is made up of a soft and fluffy vegan vanilla sheet cake base, topped with dreamy swirls of mixed berry buttercream frosting.  All you need is one bowl, any type of frozen berries you desire, and a handful of pantry staples, and you’ll be impressing friends and family with this beauty in no time!

Friends, I have a lot to say about this cake.  Which I am going to say in the very next line.  But I am going to start with – LOOK. AT. THOSE. SWIRLS.  Look at those things!!!  I think if you look too long you may get hypnotized, and that’s not my goal here.  My goal is to help you bake a really yummy vegan vanilla sheet cake.  So let’s get back to that.

Okay, this cake.  It’s delicious!  The cake itself is SO soft and fluffy, and super tender and moist thanks to a great mixture of vegan butter AND oil.  The frosting color is natural, thanks to a concentrated reduction of frozen berries mixed into a traditional vegan buttercream frosting recipe.  You can even toss some fresh berries on top for an added pop of flavor and texture.

The fun of this cake is how versatile it is.  Since the berry frosting is made using frozen berries, you can pick any type of frozen berry you want and customize your flavor that way.  If you love a little lemon brightness with fruit flavors, feel free to add some lemon zest into the base of the cake (follow along with this Lemon Sheet Cake recipe if you want to mix and match the cake base and the frosting).  If you have fresh berries on hand, you can add some over the top like I mentioned earlier.  Or just make the cake to snack on. You can’t go wrong with a delicious vanilla cake hanging out on the counter to pick at between meals!

Okay the last thing I’ll say before we get into the step by step is – LOOK AT THOSE FROSTING SWIRLS!!

How To Make It:

This cake is easy easy easy.  It’s got two components – the vegan vanilla sheet cake itself, and the frosting.  We’re going to start with the frosting, simply because the berry reduction will need time to cool before mixing it in with the frosting, so that’s where you’ll want to start your journey today.

The berry reduction..

Start by measuring out 2 cups of frozen berries.  You can certainly use fresh berries if you want, but I recommend frozen since they’re just getting mashed into liquid anyway. May as well save the money and use any fresh berries for topping instead.  And again, you can use any type of frozen berries you want here – raspberries, strawberries, blueberries, blackberries.. I used a mixed berry medley of all 4 for the photos you see in this post.  Put your frozen berries into a small saucepan or pot with 2 tbsp of sugar (see the Ingredients Needed section to learn how to make this whole cake sugar free!) and heat on medium/low heat for 10-15 minutes.  During this time, break up the berries as much as possible using a wooden spoon or spatula or fork.  Keep at it until there are no big chunks left.

Once they’re pretty liquified, strain the liquid out through a fine mesh strainer.  It will come to around 1/3 of a cup (don’t forget to measure liquid in liquid measuring cups!), but don’t worry if it’s a little more or a little less, we can balance this out later with how much powdered sugar we add into the frosting itself.  Set the liquid aside to cool entirely before taking next steps with it.

The cake batter..

While the berry liquid is cooling, it’s cake time!!  The best time!  Make sure your vegan butter and non-dairy milk are at room temperature before beginning here – I leave mine out for 2-3 hours before starting.  In a large bowl, combine the vegan butter, neutral oil, and sugar.  You want to cream this together fully until it is light and fluffy.  Whether you are using a stand mixer, hand mixer, or just getting down and dirty with your hands, do not skimp on this part.  Mix it for a solid few minutes until it looks like the below.

Next add in the other wet ingredients, the non-dairy milk and vanilla extract.  At this point the mixture will look separated, sort of like a weird oil painting.  This is okay and correct, and it will come back together again with the dry ingredients, which you will add in next.  Gluten free (or all-purpose) flour, baking powder, and salt.  Mix until fully combined, but try not to overmix or the batter will get tough.

Pour into a well-greased and/or parchment lined 9×13 pan, and bake at 350 degrees for 30 minutes.  I turn the pan halfway through the bake time to ensure it bakes evenly on all sides, which I recommend for you too unless you know your oven is the most perfect oven of all time and there are no warmer spots or cooler spots.  Test for doneness by sticking a toothpick into the center of the cake and removing from the oven when the toothpick comes out with just crumbs, no wet batter.

Place the pan directly onto a cooling rack to make sure air circulates around the bottom as well, and let cool in the pan for at least 15-20 minutes before removing it.  Even if you used parchment paper I’d recommend removing by inverting the cake out onto a large cooling rack or large pan or cutting board or anything it’ll fit onto, since if you try to lift out using the parchment paper it may break in the middle.

The frosting..

You want the cake to cool entirely before frosting it, which works well because your berry concentrate probably needs a bit more cooling time too.  When they’re both at room temperature, it’s time to make the frosting.  Start by adding the vegan butter to a large bowl, you want it cold straight from the fridge.  Beat it for a few minutes until it’s soft and fluffy, I use a simple hand mixer, but of course you can use a fancier mixer if you’ve got one. 

Add in the powdered sugar and the berry liquid a little bit at a time mixing and scraping down the sides along the way to combine it all together.  I’d also suggest tasting as you go, since depending on the berries you used / the amount of liquid you get / etc, you may want to adjust slightly.  If you want a thicker frosting, add more powdered sugar.  You may want to add a pinch of salt or a tsp of vanilla extract to taste. 

And now you’re ready to put the vegan vanilla sheet cake together!  Spread the frosting on top of the cake, add some fresh berries if you want, and get to eating!  Oh and if you need cake decorating inspiration – LOOK. AT. THOSE. SWIRLS!!!

Storage:

Store the cake in an air tight container and keep at room temperature for a day or two, or in the fridge for 3-5 days.

Pro Tips & Tools:

• Make sure you are measuring your flour either by weight or using the spoon and level method.  Do not scoop directly from the container, as you will wind up with too much! This is so important! If you want to buy a pre-made gluten free flour blend, make sure it’s King Arthur’s Measure for Measure Gluten Free Flour, it is BY FAR the best one for my recipes, NOT Bob’s Red Mills or any others. If you want to make a homemade blend, here is a link to the one I use.
• Make sure you measure your liquid ingredients using liquid measuring cups.  This will ensure accuracy!  I love this set.

Ingredients Needed:

• Frozen berries – whichever type of berry you want to use.  I used a mixed berry blend in these photos.
• Powdered sugar – for the frosting. If you want this part to be sugar free, you can use this Monkfruit Powdered Sweetener in place of powdered sugar.
• Vegan butter – I use Earth Balance sticks
• Neutral oil – any should do, I always use grapeseed. 
• Granulated sugar – If you want to make these sugar free, I love using this Monkfruit Sweetener in place of granulated sugar.
• Non-dairy milk – any should do here!  I usually use soy or almond.
• Vanilla extract
• Flour – Make sure you are measuring your flour either by weight or using the spoon and level method.  Do not scoop directly from the container, as you will wind up with too much! This is so important! If you want to buy a pre-made gluten free flour blend, make sure it’s King Arthur’s Measure for Measure Gluten Free Flour, it is BY FAR the best one for my recipes, NOT Bob’s Red Mills or any others. If you want to make a homemade blend, here is a link to the one I use.
• Baking powder – I recommend using baking powder that has no added aluminum. This one is my go-to.
• Salt

What To Bake Next:

• Want more berry goodness? Try this Vegan Triple Berry Cake, or these Vegan Berry Crumble Bars, or these Super Fluffy Vegan Blueberry Muffins.
• Want more CAKE after this vegan vanilla sheet cake masterpiece? Try this Vegan Blueberry Cake with Lemon Curd Filling, or this Vegan Carrot Cake, or this Vegan One Bowl Red Velvet Cake, or this Vegan Triple Chocolate Cake.
• Want more summertime party treats? Try these Perfect Vegan Lemon Bars, or this Vegan Mimosa Bundt Cake, or this Vegan Lemon Pound Cake.