How to make a Union Jack Sponge Cake (Coronation Cake)

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This week, in Britain and all over the Commonwealth, millions of people will celebrate King Charles III’s Coronation!. All over the UK there will be parades, events and garden parties.

As Julia Child famously said ‘A party without a cake is just a meeting’ ? so I present to you, my fabulously festive Union Jack Sponge Cake. A beautiful and delicious cake perfect for a grand celebration.

Table of Contents

What is a Union Jack Sponge Cake?

Inspired by a classic British cake, the Victoria Sponge cake, my Union Jack traybake is made from two layers of light and fluffy vanilla sponge, filled with spiked custard cream and topped with fresh berries in the shape of a Union Flag.

The whole of the UK will be a sea of Union Jack Flags this weekend amidst the coronation celebrations, so why not add one to your party table?

Perfect for parties!

I have baked this sponge cake in a large rectangular baking tray, before halving the cake and stacking it on a serving plate. This method will serve 6-8 people.

If you are having a street party or feeding a big crowd, simply double the recipe and bake on two trays, or keep the cake in a single layer and serve it directly from the baking dish. You could also cut it up and make multiple small cakes for an elegant presentation.

My Never-Fail Sponge Cake Recipe

I am going out on a bit of a limb here to call this never-fail, but my easy sponge cake recipe is truly tried and tested. It will bake beautifully in loads of different sizes so if you only have a round cake tin or pan, don’t worry!

You can divide the recipe between two 20cm (8 in.) cake pans for a very high and fluffy cake, or use a 26cm (10 in.) pan for an easier to slice cake. Casserole and baking dishes work well too, just be sure to line the base and grease the sides and baking paper well.

Cake batter and whisk showing correct texture.

Ingredients

Sponge cake is made with very simple ingredients. Eggs, sugar, oil, vanilla, flour and baking powder. The homemade custard cream is actually what is known as Creme Diplomat, a mixture of vanilla custard and luscious whipped cream.

It is a wonderful, stable cake filling which looks and tastes fabulous.

Decorating This Cake

The cake is topped with seasonal berries, the perfect way to create the red and white of the Union flag. The Union Jack shape is made up of four parts:

The wide strips of the Saint George’s cross (England) are made from strawberries, forming a cross through the middle.
The thin strips of Saint Patrick’s cross (N. Ireland) are made of raspberries, crossing diagonally from corner to corner.
The cross of Saint Andrew (Scotland) is represented by the white line of the custard cream and the blue triangles of blueberries.

If you like, you could also spread the bottom half of the cake with a little raspberry jam for extra wow.

Substitutions

I always make my sponge cake with oil, rather than butter as I find it stays moister and bakes more reliably. If you do not want to use oil, you can replace it with the same amount of melted and cooled unsalted butter.
You can change the berries to suit what you have, red currants make a particularly beautiful red. Be sure to use fresh, ripe berries. Frozen are unsuitable for this recipe.
Sponge cake is great to make gluten-free, simply use your favourite gluten-free flour blend. As always, gluten-free bakes tend to be less stable, so transport carefully.

What to serve with a Union Jack Sponge Cake?

With this very British recipe, you couldn’t go wrong with a cup of tea! Of course, as there will be street parties up and down the length of the country this weekend, I suspect that a glass (bottle!) of Prosecco or sparkling wine wouldn’t go astray.

I highly recommend making the official dish of the coronation ‘King Charles’ Coronation Quiche’! or Queen Elizabeth II’s ever popular ‘Coronation Chicken’
If you are having a British inspired garden party, why not serve Scotch Eggs, Mini Cottage Pies, Puff Pastry Mini Quiches or a delicious Chicken Terrine?
If you are planning a proper sit down meal, you can’t beat my Perfect Pork Wellington or Ultra Slow Roast Beef recipes.

Frequently asked question

Can I make Union Jack Flag Cake in advance?

I often make the sponge cake the night before I need it. I leave it on the bench top, covered loosely with cling film and decorate it the following day. Once you have decorated it, it is best to eat the cake on the same day to stop it from going soggy.

Can I make this sponge cake in different sized tins?

Yes! This is a flexible recipe. It works very well divided between two 20x30cm trays, or 24-26cm round spring form cake pans. Be aware that this cake really puffs up, so you do need to use high sided baking dishes. A square tin would also work, you will need to ensure the cake is risen, golden brown and springy to the touch to make sure it is cooked through.

Can I use frozen berries on this cake?

Not this cake, sorry. They are too wet and will make the cake soggy. Also, as the wonderful Nigella Lawson always says, frozen strawberries are awful, like wet slugs!

Can I leave the alcohol out of this recipe?

Yes! Try infusing the custard with homemade elderflower cordial instead!

Can I make an extra-large version of this cake for a big party?

Yes! Double all ingredients and bake two sponges. I would bake one after the other rather than trying to use fan bake or swapping trays around in the oven. Because you are unlikely to have such a big serving dish, simply stack and serve from the tray.

The British Union Jack Flag

Is it the Union Jack or Union Flag?

If you serve this cake, you are guaranteed to have this conversation (trust me). What is known worldwide as the Union Jack is really called the Union Flag, The ‘Jack’ itself is a variation flown at sea, by the Royal Navy.

What does the Union Flag represent?

The Union Flag is the national flag of the United Kingdom, combining the heraldic crosses of three countries (England, Ireland and Scotland). Poor Wales misses out, as in 1606 when the flag was created, the Principality of Wales was considered part of England.