Rhubarb custard bars are a lovely spring treat! They’re a great way to use up an abundance rhubarb from the garden. Just sweet enough, with a sturdy shortbread crust and rich, egg-based custard wrapped around sweet-tart rhubarb.
Ingredient Notes and Substitutions
- Add strawberries: if you want your bars a bit sweeter, replace half of the rhubarb with sliced strawberries. Please note, strawberries contain more water than rhubarb so the custard may take longer to set in the oven.
- Add-ins: add lemon zest, orange zest, or a teaspoon of finely chopped or grated fresh ginger to the custard if you like.
- Make it dairy-free: use a good quality vegan butter.
- To make gluten-free custard bars: sub a good GF flour blend (like the Bob's Red Mill one) for the all-purpose flour. There are probably other flours that will work as a shortbread base since it doesn't need to rise, but we haven't tested any.
Step 1: beat the butter and sugar until light and fluffy.
Step 2: mix in the flour and salt to make a crumbly dough.
Step 3: press the shortbread dough into a lined square baking dish and bake. Set aside.
Step 4: mix the sugar, eggs, and egg yolks until smooth.
Step 5: mix in the dry ingredients until smooth and scrape down the sides of the bowl.
Step 6: fold in the chopped rhubarb.
Step 7: pour the rhubarb mixture over the shortbread base.
Step 8: bake until set and cool before serving.
- Peel the rhubarb: If your rhubarb is older or the stalks are really thick, peel them for the best taste.
- Cool before slicing: the bars need to be fully cool before cutting into squares because the custard is still too soft when it's warm.
- Eat when fresh: custard bars don't freeze well as a general rule, so plan to make these when you can eat the whole batch in a day or two.
Don’t worry if your custard turns light gold in places while baking—this is normal!
Frozen rhubarb will work here, but you may need to bake the bars a bit longer. The custard texture will change slightly due to the extra water in frozen rhubarb, but it works in a pinch. Don't thaw if using frozen fruit.
It's pretty important to let the bars cool before slicing because the custard needs time to set. If you cut them too soon, you'll end up with oozy custard and slices that aren't neat.
How to Store Rhubarb Bars
Storage: place the sliced bars in an airtight container and store at room temperature for the first day. After that, store the container in the fridge. Baked custard doesn't store fabulously, and can make the shortbread soggy.
Freezing: These bars don't freeze well so eat them within a couple of days.
Do you have to peel rhubarb?
The simple answer is no, you don't. That being said, if your rhubarb is older, tough, and woody, peeling the outside with a vegetable peeler will leave behind the more tender inside of the stalks.
How long does it take to bake rhubarb bars?
We bake the shortbread crust first until golden, about 24 minutes because we like a slightly crisp snap to the crust. We bake the crust with the custard topping for 42 to 45 minutes. Baking time depends on your oven (we recommend using an oven thermometer!), and whether or not you are using fresh or frozen rhubarb.
Can you freeze rhubarb squares?
Freezing the bars will change the texture of the custard, making it too soft and weepy when it thaws. We don't recommend freezing these.
If you make this Rhubarb Custard Bar recipe or any other spring baking recipes on the Baked Collective, please take a moment to rate the recipe and leave a comment below. It’s such a help to others who want to try the recipe. For more baking, follow along on Instagram, TikTok, and YouTube.
Rhubarb Custard Bars (One Bowl)
- Oven thermometer we can't recommend this enough for all of your baking!
- 8 or 9-inch (20 or 23-cm) square baking dish
- Mixing bowl
- Hand or stand mixer
- Measuring cups and spoons or a digital kitchen scale
- Rubber spatula or wooden spoon
- Parchment paper
- Wire rack
For The Crust
- ½ cup butter plus 2 tbsp, room temperature to soft
- ¼ cup sugar
- 1 ¼ cup all-purpose flour
- ¼ teaspoon salt
For The Custard
- ¾ cup sugar
- 1 large egg plus 2 egg yolks
- ¼ cup all-purpose flour
- ¼ teaspoon salt
- 3 cups rhubarb fresh or frozen, chopped into 1-inch (3-mm) pieces
Make The Shortbread Crust
- Preheat the oven to 350ºF (180ºC) and line an 8 or 9-inch (20 or 23-cm) square baking dish with parchment paper.
- In a mixing bowl, beat the butter and sugar together until light and fluffy, about 1 to 2 minutes.
- Add the flour and salt, and continue to mix on low until the dough is crumbly with no visible flour remaining.
- Dump the dough crumbs into the prepared baking dish. Use your hands to first spread, then press the crust evenly into the pan creating a tightly packed shortbread layer.
- Place the crust into the preheated oven for 24 to 26 minutes or until the edges turn slightly golden. Remove the crust from the oven and place it on a wire cooling rack.
Make The Custard
- While the crust is in the oven, make the custard. Using the same mixing bowl, combine the sugar, egg, and yolks. Mix everything together on low speed until smooth.
- Add the flour and salt to the mixture and continue to mix on low until no visible streaks of flour remain, scraping the sides of the bowl down halfway through mixing.
- Add the chopped rhubarb to the custard and fold it in gently until well coated.
- Pour the rhubarb custard mixture over the pre-baked shortbread crust. Use a rubber spatula or fork to spread the rhubarb into an even layer.
- Place the baking dish back in the oven and bake the rhubarb custard bars for 42 to 45 to minutes, or until the custard is set. Place the baking dish on a wire rack and cool the bars completely before slicing.