Flaky gluten-free shortcrust pastry, velvety vegan vanilla custard and jammy rhubarb come together in this gluten-free and vegan rhubarb custard tart to make your dessert dreams a reality!
Never in your wildest dessert dreams did you imagine that the words vegan and gluten-free would be followed by custard tart, but this recipe for a rhubarb custard tart is a dream come true!
Silky smooth vegan vanilla custard topped with jammy lemon spike rhubarb encased in a flaky gluten-free shortcrust pastry is the showstopper of a summer dessert you’ve been waiting for.
Whether you’ve got friends to impress, frenemies to show up, or you’re on a mission to convert some omnivores to veganism this tart is the solution! Make it, dream about it and good luck sharing it!
What do you need to know before you make this recipe?
There are multiple stages to this recipe, so you’ll need to put a block of 2-3 hours aside. Start by soaking the cashews for the custard, then make the pastry, followed by the rhubarb and lemon compote. At this point, the cashews will be soft enough to blend, and you can move on to making the custard.
When you’re ready to assemble the custard should be hot, so you’ll need to work quickly. Pour the custard straight from the pot into the pastry case and then let it set in the fridge before adding the rhubarb and serving.
I’ve included all the additional notes for this vegan rhubarb custard tart recipe at the bottom of the page with the hope of improving your experience here at blue border. If you found this useful, I’d love your support on Instagram, click here to follow.
For the pastry
- 275g / 9.7oz gluten-free flour, all-purpose
- ¾ tsp. xanthan gum
- ¼ tsp. fine sea salt
- 1 Tbsp. caster sugar
- 180g non-dairy butter, cold and cut into cubes
- 1-4 Tbsp. cold water
For the rhubarb compote
- 500g / 1.1lb rhubarb, roughly chopped
- 1 large lemon, zest and juice
- 125g / 4.4oz caster sugar
For the custard
- 250g / 8.8oz raw cashew nuts
- 350g / 12.35oz boiling water
- 60g / 2.1oz cornstarch
- ⅛ tsp. fine sea salt
- 150g /5.3oz caster sugar
- 1 x 400ml / 14oz tin coconut cream
- 1 vanilla pod or 2 tsp. vanilla bean paste
- 1 Tbsp. non-dairy butter
Start by submerging the cashews in boiling water and set aside for 1 hour (the longer you leave the cashews to soak, the smoother the custard will be, so if you have the foresight, this can be done the day before).
Make the pastry.
Preheat the oven to 160C. Grease a 24cm loose bottom tart tin and line the base with a round of parchment paper.
Place the flour, xanthan gum, salt and sugar in the food processor and pulse to combine. Add the butter to the flour and pulse into a texture that resembles coarse bread crumbs (if you’re using non-dairy margarine instead of butter, you may find that after a few pulses, a dough forms).
Add one tablespoon of water at a time, pulsing the mixture between each addition of water, until the pastry comes together into a smooth ball. Depending on the brand of flour and butter you use your pastry may need more or less water.
Generously dust a work surface with flour and roll out the pastry into a large round approx. 3mm thick. Gently roll the pastry onto the rolling pin, transfer it to the tart dish and shape the pastry along the sides of the tin (if you find your pastry cracking excessively, add more water until it’s easy to roll out and shape). Trim the edges of the pastry and prick the base with a fork. Place a piece of parchment over the pastry base, fill with baking beads and blind bake for 30mins.
When the pastry is ready, remove the parchment paper and baking beads and allow it to cool while you make the fillings.
Make the rhubarb compote.
Combine all the ingredients in a saucepan, mix briefly and bring to a gentle simmer for 10mins or until the rhubarb is tender. Remove the pan from the heat and set it to one side.
Make the custard.
Transfer the soaked cashews, soaking water, cornstarch, salt, caster sugar and coconut cream to a high-speed blender and blend until completely smooth (if you have a small blender, you can add the caster sugar and coconut cream straight to the pot instead).
Pour the blended mixture into a large pot and place on the hob on low heat. Stir the custard continuously for 20minutes or until the custard has thickened and easily coats the back of a spoon. Continuous stirring will prevent the custard from burning or getting lumpy, use a rubber spatula to prevent a skin from forming on the bottom of the pot and contributing to lumps.
Add the seeds from the vanilla pod and non-dairy butter to the custard just before removing it from the stovetop and stir until the butter has completely melted.
Immediately pour the custard into the pastry base, use an offset spatula to smooth it out and place the tart in the fridge for one hour to set. Gently spoon the rhubarb over the top of the tart before serving.
NOTES: Vegan Rhubarb Custard Tart
I use Dove’s Farm gluten-free flour for this vegan rhubarb custard tart recipe and love the way it performs.
If you’re in the US try Bob’s Red Mill One for One gluten-free flour, King Arthur’s all-purpose gluten-free flour or Better Batter.
Xanthan gum (what is it and do I have to use it?)
Xanthan gum is a binder made through the process of fermenting simple sugars. In this recipe, xanthan gum helps hold the pastry together in the absence of natural binders like eggs and gluten.
I have only tested the pastry recipe with xanthan gum so if you choose not to use it I can’t guarantee it’ll work.
You will get the best results from the pastry and the custard by using solid vegan butter. In the UK and Europe try Naturli Vegan Block or Flora Plant Butter. In the US I know the solid vegan butter brands are Earth Balance, Miyoko or Country Crock Plant Butter.
The best kind of coconut cream for this recipe is one that has a thick layer of solid cream at the top. Try shaking the tin while you’re in the store – you’re looking for one that sounds solid rather than liquidy.
I highly recommend you use the seeds from a vanilla pod for this recipe. Not only does it give the custard a gorgeous fresh vanilla flavour you’ll also get that beautiful vanilla speckle.
If you can’t find fresh vanilla pods, then try vanilla bean paste.
Why is my pastry cracking and crumbling?
You left out the xanthan gum. As previously mentioned, xanthan gum is a binder that holds gluten-free doughs together in the absence of gluten or eggs.
Your pastry needs more liquid. It’s surprising how much liquid gluten-free flour absorbs and, pastry dough that’s cracking or crumbling is a good indicator that you need to add more water. Add one tablespoon of water at a time until your dough rolls out easily.
Eeeeee my custard is lumpy, what should I do?!
This custard is thickened with cornstarch, which tends to form lumps if left to its own devices, so keep the heat low and DON’T STOP STIRRING!
If you have a few small lumps in your custard, don’t worry too much, they might not look great, but they don’t affect the texture.
If you have a lot of lumps, you can sieve your custard or reblend it. However, if you reblend the custard, you will have to thicken it again. Wash your pot, add the custard and stir continuously on low heat until you achieve the desired consistency.