Rhubarb Mug Cake
Some nights you want cake, not a whole baking project. That’s the entire case for a mug cake — one bowl, one mug, no oven, done before the kettle’s finished boiling. This version uses leftover cooked rhubarb and a hit of cinnamon, so it tastes like something you actually planned rather than something you threw together out of desperation at 9pm. Which, let’s be honest, is usually how mug cakes happen anyway.
Why This One Works
Rhubarb is tart, and tart against a soft, cinnamon-warmed sponge is a good pairing — it’s basically the same logic behind rhubarb crumble, just shrunk down and sped up. If you’ve got a spoonful of stewed rhubarb sitting in the fridge from a bigger batch, this is exactly what to do with it. No need to cook rhubarb specially for one mug cake; use what’s already there.
Ingredients
Gather your ingredients and get ready for a quick treat! No baking powder needed separately since self-raising flour already has it built in, and no butter to soften or melt.
- Self-raising flour – Gives the cake its light, fluffy texture.
- Sugar – Sweetens the cake and balances the tartness of the rhubarb.
- Milk – Adds moisture and helps create a smooth batter.
- Egg – Provides structure and richness.
- Vegetable oil – Keeps the cake soft and moist.
- Ground cinnamon – Adds warmth that pairs beautifully with rhubarb.
- Cooked rhubarb – Brings a delicious tangy flavour and soft texture.
How To Make Rhubarb Mug Cake
Mix the egg, oil and milk in a mug
Stir in the flour, sugar and cinnamon and mix.
Spoon in the cooked rhubarb.
Microwave for 90 seconds.
Recipe Tips
Don’t overfill your mug. Use one that’s at least 12 ounces (350ml). Cooking times vary by microwave wattage. Start checking after 90 seconds. Avoid overcooking, as the cake can become dry. Make sure the rhubarb has been cooked first, as raw rhubarb won’t soften enough during microwaving. Let the cake stand for one minute after cooking for the best texture.
Getting the Texture Right
The most common mug cake failure is overcooking, which turns the whole thing rubbery. Microwaves vary a lot — an 800W and a 1000W will need different timings for the exact same recipe — so treat the time above as a starting point, not a rule. Pull it out a touch early if you’re unsure; a slightly underdone centre is easy to fix with another 10 seconds, but a rubbery cake can’t be undone.
Swaps and Variations
- No cooked rhubarb on hand? Raw rhubarb, finely diced, works too — it just won’t be quite as soft, and you may want to add a pinch more sugar to balance the extra tartness.
- Swap the cinnamon for ground ginger if you want something sharper alongside the rhubarb.
- A small spoon of vanilla yogurt or a splash of cream on top turns this from “snack” into “actual dessert.”
Can You Make This Ahead?
Not really, and that’s kind of the point. Mug cakes are best eaten within a minute or two of coming out of the microwave — the texture firms up and dries out fast once it cools. Mix the dry ingredients in advance if you want a head start, but add the wet ingredients right before cooking.
What to Serve with Rhubarb Mug Cake
This mug cake is delicious on its own, but you can also serve it with:
- Vanilla ice cream
- Whipped cream
- Custard
- Greek yogurt
- A drizzle of honey
- Extra cooked rhubarb
- Chopped toasted almonds
More Mug Cake Recipes You’ll Love
FAQs
It needs to be microwave-safe — ceramic or glass without metallic trim. Skip anything with a gold or silver rim.
You’d need a small ramekin and about 12-15 minutes at 180°C (350°F), but at that point you’re basically making a mini baked pudding rather than a mug cake. The microwave version is faster and the reason most people make these in the first place.
Too much batter for the mug, or a mug that’s too narrow. Use a mug that’s at least 350ml and don’t fill it more than halfway before cooking.
These timings work best in an 800–1000W microwave. Lower-powered microwaves may need an extra 15–30 seconds.
No. Mug cakes are best eaten fresh as freezing changes their texture.
Rhubarb Mug Cake
Need Metric Measurements?
Use the button options below to toggle between US cups and Metric grams.
Ingredients
- 4 tablespoons self raising flour
- 2 tablespoons sugar
- 3 tablespoons milk
- 1 medium egg
- 1 tablespoon vegetable oil
- 1/2 teaspoon cinnamon
- 2 tablespoons cooked rhubarb
Instructions
- In a microwave safe mug, add the egg and beat. Add the milk and oil and mix.
- Add the flour, sugar and cinnamon. Stir until smooth — don't worry about a few small lumps, they'll cook out.
- Fold in the diced cooked rhubarb, keeping a few pieces back if you want to press them into the top for looks.
- Microwave on high for 1 minute 30 seconds to 2 minutes, depending on your microwave's wattage. Start at 90 seconds and add 15-second bursts until the centre springs back when touched.
- Let it sit for a minute before eating. It's genuinely lava-hot straight out of the microwave.
Video
Notes
Nutrition
The information shown is an estimate provided by an online nutrition calculator.
