Picture a crisp, buttery shortbread base topped with a silky, golden custard and ribbons of tart pink rhubarb that turn jammy in the oven. One bite gives you crumbly crust, creamy filling and a bright little zing that keeps every square from feeling too sweet.
These bars are perfect for the first weeks of spring when rhubarb stalks show up at the farmers market. They travel well, slice neatly once chilled, and feed a crowd, so they fit brunches, potlucks, baby showers and Mother's Day tables beautifully.
SaveMy grandmother grew rhubarb along the back fence and always said it was the only plant that could survive anything. She baked a custard pie with it every May, and these bars are my easier, hand-held spin on her pie that I can make in one pan.
Rhubarb Custard Bars
Ingredients
Shortbread Crust
Rhubarb Layer
Custard Filling
Instructions
- Prep the pan
Preheat the oven to 350°F. Line a 9x9-inch baking pan with parchment paper, leaving an overhang on two sides so you can lift the bars out later, and lightly grease the paper.
- Make the crust dough
In a medium bowl, whisk together 1 1/2 cups flour, the powdered sugar and 1/4 teaspoon salt. Add the cold cubed butter and rub it in with your fingertips or a pastry cutter until the mixture looks like coarse crumbs and holds together when pinched.
- Press and bake the crust
Press the crumbs firmly and evenly into the bottom of the pan, using the flat bottom of a measuring cup to smooth the surface. Bake for 18 to 20 minutes until the edges are lightly golden. Leave the oven on.
- Toss the rhubarb
While the crust bakes, stir the sliced rhubarb together with 1/2 cup sugar and the cornstarch in a bowl. Let it sit for about 10 minutes so the sugar draws out some juices and the cornstarch dissolves into them.
- Whisk the custard
In a large bowl, whisk the eggs and 3/4 cup sugar until smooth and slightly pale. Whisk in the sour cream, heavy cream, 3 tablespoons flour, vanilla and 1/4 teaspoon salt until no lumps remain. The custard should be thin and pourable.
- Layer the rhubarb
Scatter the rhubarb over the warm crust in an even layer. Spoon only about 2 tablespoons of the juices from the bowl over the top and discard the rest, which keeps the bars from turning soggy.
- Pour on the custard
Slowly pour the custard over the rhubarb, nudging the fruit with a spoon so the liquid fills every gap. Tap the pan gently on the counter to release any air bubbles.
- Bake until just set
Bake for 35 to 40 minutes, until the edges are set and the center jiggles only slightly when you nudge the pan. The top should be pale golden with a few browned spots. Do not overbake, or the custard can turn rubbery.
- Cool completely
Let the pan cool on a wire rack for 1 hour at room temperature, then cover loosely and refrigerate for at least 3 hours, or overnight. Chilling is what firms the custard so it slices cleanly.
- Slice and serve
Lift the slab out using the parchment overhang and set it on a cutting board. Use a sharp knife wiped clean between cuts to slice it into 16 bars. Dust with powdered sugar just before serving if you like.
Substitutions and variations
- Frozen rhubarb works well if you thaw it and pat it very dry first, so the extra liquid does not make the custard watery.
- Swap the sour cream for plain full-fat Greek yogurt for the same creamy tang.
- Replace half of the rhubarb with sliced strawberries for a sweeter, rosier bar.
- Add the zest of one orange to the custard for a fresh citrus note that loves rhubarb.
Chloe's tips
- Use firm, bright stalks of rhubarb and trim off any leaves, which are not safe to eat.
- Cut the rhubarb into even pieces so every bite cooks at the same pace and softens in the same time.
- Keep the butter cold for the crust so it bakes up crisp and tender instead of greasy.
- A sharp, clean knife dipped in hot water and wiped dry gives you the neatest edges.
How to store it
- Store the bars in an airtight container in the refrigerator for up to 4 days.
- Because of the custard, do not leave them at room temperature for more than 2 hours.
- To freeze, wrap individual bars tightly and freeze for up to 1 month, then thaw overnight in the refrigerator.
Serving suggestions
These bars are lovely cold or slightly cooled, and they shine with a simple topping or a hot drink alongside.
- Dust with powdered sugar for a pretty finish.
- Add a spoonful of lightly sweetened whipped cream.
- Serve with fresh strawberries on the side.
- Pair with hot coffee or a pot of Earl Grey tea.
Frequently asked questions
Why is my custard layer watery?
Rhubarb releases a lot of juice as it bakes. Tossing it with cornstarch, spooning on only a little of the juices, and patting thawed frozen rhubarb dry all keep the filling set.
Can I make these rhubarb custard bars ahead of time?
Yes, they actually taste better the next day. Bake and chill them overnight, then slice just before serving.
How do I know when the custard is done?
The edges should look set and the center should wobble just a little, like gelatin. It firms up fully as it chills in the refrigerator.
Can I use a different pan size?
A 9x13-inch pan works if you double the recipe. For a single batch, stick with an 8x8 or 9x9-inch pan so the layers stay thick enough to slice.
Let's get cooking!
Whether you bake these for a spring gathering or just because the rhubarb is calling your name, they are a sweet reminder that tart and creamy belong together. Grab a bunch of fresh stalks, give the recipe a try and enjoy every silky, tangy bite.
