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Oat Flour Rhubarb and Custard Cake

A dessert flavoured rhubarb and custard cake made with homemade oat flour. This cake is suitable for vegetarians but not vegans.

Oat Flour Rhubarb and Custard Cake


This fluffy cake is full of roasted rhubarb and custard and it's utterly glorious.

The custard is mixed into the cake batter and more is added to the top of the cake.

It's good served as it is or warmed up and served with yet more (hot) custard.

You don't eat custard cold do you? 

I have this argument with my husband all the time. He always eats it cold which I think is just plain wrong!

Vegan? I'm working on a vegan version of this cake, but it needs a bit more work. I'll share it when it's ready.

oat flour


I've been experimenting with oat flour recently and this is the second cake I've made with it and they have both come out really well.

So far I have used mostly oat flour with some plain flour added to lighten the mixture, but I haven't tried all oat flour yet, so that will be my next experiment.

Using oat flour in a mix of oat and plain is a great way to make plain flour last longer if you are running out.


Oat flour is super simple to make at home.

Just pop your oats into a blender or food processor and whizz until you have a fine flour. It's easy!

You can use porridge oats (also known as rolled oats), fine oatmeal or jumbo oats to make oat flour. Basically any oats you have.

You can use them in cakes, flatbread, pizza dough, brownies, cookies ....... Yes the list is endless.


The special thing about oats is they are full of slow release energy. They are also high in protein, vitamins and minerals.

Hamlyns Porridge OatsI use Hamlyn's of Scotland oats for breakfast and in my recipes. Their oats are really good quality, 100% natural with no added salt, sugar or additives.

Hamlyns are a family business who have been milling premium Scottish oats since 1888 and their products are sold in all good supermarkets.

They mill porridge oats, porridge oats with bran (10% wheatbran added), oatmeal and pinhead oatmeal.

Check out the Hamlyn's website for all their oat recipes for more inspiration.

stalks of rhubarb


Oh how I love rhubarb.

I love it just cooked, yes it's lucky if it makes it into a dish. I love it in a rhubarb crumble, in a pie, in a cake like this or with yoghurt.

Forced rhubarb is available from January to March and the main crop is available from April to June. Of course frozen rhubarb is available all year round.

chopped rhubarb in ovenproof dish


Rhubarb is chopped into 2-3 cm/1 inch pieces, then dusted in sugar before it is roasted lightly in the oven to soften and sweeten it.

I didn't use a lot of sugar when roasting my rhubarb, but if your rhubarb is particularly sour once roasted, you may add extra sugar and mix.

Once the rhubarb is cooked, it needs to be spooned onto kitchen paper to drain the juice.

If you don't drain the rhubarb, too much liquid could spoil your cake. It won't be light and fluffy but stodgy. It will still taste good and be fine heated as a pudding, but disappointing as a cake, so don't skip this step.

Rhubarb and Custard Cake dusted with icing sugar


Ready made custard is added into the batter or this cake and added to the top of the cake before it is baked.

You could use fresh chilled custard, homemade custard (it needs to be quite thick) or tinned custard. All will work well.

If you have leftover custard, you could warm slices of your baked cake and serve it with the custard.

Oat Flour Rhubarb and Custard Cake


  1. Strawberry & Rhubarb Crumble
  2. Scottish Rhubarb & Berry Crumble
  3. Rhubarb & Orange Jam
  4. Strawberry & Rhubarb Jam
  5. Potato Salad with Rhubarb & Balsamic Dressing
  6. Rhubarb Pudding
  7. Rhubarb Crumble Ice Cream
  8. Slow Cooker Rhubarb Cobbler
  9. Vegan Rhubarb & Custard Sponge Pudding

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Oat Flour Rhubarb and Custard Cake. A fruity cake which is light and fluffy. Good served warm with custard for a family pudding. A tasty fruity dessert. #rhubarb #custard #oatflour #oatflourcake #fruitcake #rhubarbcake #custardcake

Oat Flour Rhubarb and Custard Cake

Oat Flour Rhubarb and Custard Cake
Yield: 8 - 10
Prep time: 10 MCook time: 1 hourTotal time: 1 H & 10 M
A dessert flavoured rhubarb and custard cake made with homemade oat flour made from porridge oats whizzed up in a blender or food processor. This cake is suitable for vegetarians but not vegans.


  • 400g/14 oz fresh rhubarb stalks (no leaves)
  • 2 tbsp caster sugar
Cake Batter
  • 250g/1 cup butter
  • 150g/3/4 cup caster sugar
  • 4 large eggs
  • 1 tsp vanilla extract
  • 150g/1 cup ready-made custard, plus extra to decorate
  • 150g/ 1 1/4 cups oat flour (Hamlyn porridge oats quickly blended into flour in a blender or food processor)
  • 100g/3/4 cup & 1 tbsp plain flour
  • 3 tsp baking powder
  • A pinch of salt


How to cook Oat Flour Rhubarb and Custard Cake

  1. Heat the oven to 180c/160c fan/350f/gas mark 4.
  2. Line a deep 8 inch/20cm loose bottom cake tin with a cake liner or non-stick baking paper.
  3. Chop the washed rhubarb into 1 inch/2 ½ cm pieces and spread out in an ovenproof dish.
  4. Sprinkle with the caster sugar and cover the dish with foil. Bake for 20 minutes until the rhubarb is soft.
  5. Spoon the rhubarb onto kitchen paper to soak up any excess liquid.
  6. While the rhubarb is cooling, make the cake batter. Start by adding the butter and sugar to a large bowl and beating with a hand or electric whisk until soft.
  7. Add the eggs and vanilla and beat again, then whisk in the custard.
  8. In another bowl mix together the two flours, the baking powder and salt, then add to the wet ingredients and whisk.
  9. Pour the batter into the cake tin in layers, adding the drained and cooled rhubarb between the layers, reserving some for the top.
  10. Once all the batter is in the tin and the top is smooth, scatter the remaining pieces of rhubarb, then add 3 or 4 dollops (tablespoons) of custard to the top between the rhubarb for decoration. No need to be too careful.
  11. Bake for 40-45 minutes until a skewer comes out clean then move to a baking rack to cool before removing from the cake tin.
  12. Serve and enjoy!


You may use frozen rhubarb, follow the same steps.
This cake is good served warm as pudding with any leftover custard or ice cream.
If you have run out of plain flour, you can use just oat flour, but the cake may be a little denser.
Fat (grams)
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rhubarb cake, rhubarb and custard, custard cake, oat flour recipe, substitute for plain flour, cake, fruit cake, pudding cake, rhubarb, custard, oats, oatmeal, porridge oats
Created using The Recipes Generator

Disclosure: I created this recipe for Hamlyn's of Scotland. I was not expected to write a positive review and any opinions expressed are my own.


  1. Oh wow! This looks delicious. I'm definitely going to have to give this a shot this week!

  2. I love rhubarb and always have some in the freezer. I will be trying this recipe, it looks wonderful.

    1. Oh me too but none in my freezer at the moment unfortunately, but I did manage to get some fresh. Do enjoy it Angela.

  3. How gorgeous is this. Love the combination and texture. So yummm

  4. I am one of the people who have run out of flour and haven't been able to get any so I am excited by this idea. Thanks for suggesting it Jaqueline I will be trying a cake with it today. Jill

    1. I am happy to help Jill. Let me know how you get on.

  5. Love the fact that it's rhubarb season. I am looking forward to trying this recipe!

    1. Yes happy days. Now we just need to wait on berry season, hope there are people looking after those plants now while we are all at home.

  6. I have never had a cake with rhubarb! This looks and sounds amazing.. definitely make it when I get my hand on rhubarb in the grocery stores near me.

    1. Oh it works so well in cake and puddings Soniya, you really must try it. I could eat the lot once it is cooked.

  7. I'm a huge fan of home made oat flour as I'm GF. You can use it for most things - pancakes, waffles etc I'll be trying this once I get some rhubarb from the allotment.

    BTW I keep meaning to say that my mum was best friends with your MIL Jean at school. She once mentioned that you had a blog and I said 'I know it, I've been following it for years!!' Small world :-)

    1. Ah that is good to know re the recipes. Must try some waffles.

      Yes it is a small world, imagine that. Thanks so much for being such a loyal reader, you have made my day Ali x

  8. your cake sounds delicious - I love rhubarb and custard - though am not so keen on cold custard except in a cake. I think when I drain the rhubarb I would use a sieve and glass and top up my rhubarb syrup with soda water - have had a few really nice rhubarb sodas in cafes.

    1. Oh my nice tip re the juice, I just scooped it up greedily with a spoon lol!

      I am totally with you about cold custard. It works in this cake for the flavour, but eating cold custard on it's own or poured over something. No! I have this discussion with my husband and son all the time as they like it cold. It's just wrong!

  9. This looks great - I am going to start making and using oat flour in some of my favourite recipes too.


I love reading comments, so thank you for taking the time to leave one. Unfortunately, I'm bombarded with spam, so I've turned on comment moderation. I'll publish your comments as soon as I can and respond to them. Don't panic, they will disappear when you hit publish. Jac x