Craving a delightful spring or summer dessert that balances tartness with creamy sweetness? These Sweet Tangy Rhubarb Custard Bars are the perfect solution, offering a buttery shortbread crust topped with a rich, vibrant custard and flavorful rhubarb. They are a showstopper dessert that is surprisingly simple to make.

Why You Will Love This Recipe

These Sweet Tangy Rhubarb Custard Bars hit every desirable note in a baked good. You get the incredible textural contrast between the crisp, buttery shortbread base and the smooth, tender custard filling. The fresh rhubarb provides that signature zing—a bright, tangy counterpoint to the sweet vanilla custard that tastes like pure springtime comfort. They are perfect for holidays, potlucks, or simply enjoying with an afternoon cup of tea.

Ingredients

• For the Crust:
• 1 cup (2 sticks) unsalted butter, softened
• 1 cup granulated sugar
• 2 1/2 cups all-purpose flour
• 1/2 teaspoon salt
• For the Filling:
• 3 large eggs
• 1 1/2 cups granulated sugar
• 1/4 cup all-purpose flour
• 2 tablespoons cornstarch
• 1/2 teaspoon vanilla extract
• 1 cup whole milk
• 2 cups fresh or frozen rhubarb, chopped into 1/2-inch pieces
• Powdered sugar, for dusting (optional)

Step-by-Step Instructions

1. Preheat the oven to 350°F (175°C). Grease and line a 9×13 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
2. Prepare the Crust: In a large bowl, cream together the softened butter and 1 cup of sugar until light and fluffy. Gradually mix in the 2 1/2 cups of flour and salt until just combined. The mixture will resemble coarse crumbs.
3. Press the crust mixture evenly into the bottom of the prepared baking pan. Bake for 15 to 18 minutes, or until the edges are just beginning to turn light golden brown. Remove from the oven and set aside while you prepare the filling.
4. Prepare the Filling: In a medium bowl, whisk together the 3 eggs, 1 1/2 cups of sugar, 1/4 cup flour, and cornstarch until completely smooth. Whisk in the vanilla extract and the milk until fully incorporated.
5. Gently stir the chopped rhubarb pieces into the custard mixture.
6. Pour the rhubarb custard mixture evenly over the warm, pre-baked crust.
7. Return the pan to the oven and bake for an additional 35 to 45 minutes. The custard should be set (it will wobble slightly in the center when gently shaken, but not liquid).
8. Allow the bars to cool completely on a wire rack before cutting. Cooling fully is essential for clean slices.
9. Once cooled, lift the bars out of the pan using the parchment paper overhang. Dust lightly with powdered sugar, if desired, and slice into squares.

Expert Tips / Pro Tips

Use room temperature ingredients, especially the butter for the crust, to ensure a smooth, evenly mixed base that bakes up tenderly.

Do not overbake the custard layer. The bars set up more firmly as they cool. If you wait until the center is completely firm while in the oven, they may become rubbery.

If using frozen rhubarb, do not thaw it first. Toss the frozen pieces directly into the custard mixture; the extra liquid will incorporate fine during the longer baking time.

For the cleanest cuts, chill the completely cooled bars in the refrigerator for at least two hours before slicing. Use a large, sharp knife, wiping the blade clean between each cut.

Variations & Substitutions

For a citrus twist, add the zest of one lemon to the custard filling. This enhances the tanginess of the rhubarb beautifully.

If fresh rhubarb is unavailable, you can often substitute with equal parts chopped strawberries in the filling for a different but equally delicious flavor profile.

For an enhanced crust flavor, substitute 1/4 cup of the all-purpose flour in the crust with almond flour for a nuttier, richer base.

Add spices like 1/4 teaspoon of ground cinnamon or nutmeg to the custard mixture for added warmth.

Serving Suggestions

These Sweet Tangy Rhubarb Custard Bars are wonderful on their own, served slightly cool. However, they pair exceptionally well with a dollop of freshly whipped cream, perhaps sweetened lightly with maple syrup.

For a richer dessert experience, serve alongside a scoop of good quality vanilla bean ice cream, allowing the cold cream to melt luxuriously over the bar.

Storage, Freezing & Reheating

Store leftover bars in an airtight container. Because of the custard filling, they must be refrigerated. They will stay fresh in the refrigerator for up to 4 days.

To freeze, place the cooled, uncut bars into a freezer-safe container or wrap tightly in plastic wrap followed by foil. Freeze for up to 3 months. Thaw overnight in the refrigerator before serving, and dust with fresh powdered sugar before enjoying.

Reheating is generally not recommended due to the custard texture, but if you prefer them slightly warm, microwave a single serving briefly (about 10-15 seconds) until just warmed through.

Nutrition Information

Note: Nutritional information is an estimate based on standard ingredient amounts and will vary based on specific product usage and serving size.

FAQ

What is the best way to tell if the custard is fully set?

The custard is set when the edges look firm and opaque, and the center has only a very slight jiggle when you gently nudge the pan. If the center looks liquid or transparent, it needs more time.

Can I use frozen rhubarb instead of fresh?

Yes, you absolutely can use frozen rhubarb. There is no need to thaw it first; just add the frozen chunks directly into the prepared custard mixture.

Why is my shortbread crust crumbly?

If your crust is too crumbly, it likely means the butter was too cold, or you didn’t mix it enough with the sugar before adding the flour. Ensure your butter is truly softened (but not melted) for the best results.

How do I prevent the rhubarb from sinking to the bottom?

Tossing the rhubarb pieces with a tablespoon or two of the flour/cornstarch mixture from the custard before stirring them into the liquid can help suspend the pieces evenly throughout the filling.

Sweet Tangy Rhubarb Custard Bars

A delightful springtime dessert featuring a buttery shortbread crust topped with a sweet and tangy rhubarb custard filling, baked until set.

Print Recipe Pin Recipe

Prep Time 30 minutes mins

Cook Time 55 minutes mins

Total Time 1 hour hr 25 minutes mins

Servings: 12 bars

Course: Baking, Dessert

Cuisine: American

Calories: 310

Ingredients Method Notes

Ingredients

  

For the Shortbread Crust

• 1 cup All-purpose flour
• 1/2 cup Unsalted butter, cold and cubed
• 1/4 cup Granulated sugar
• 1/4 teaspoon Salt

For the Rhubarb Custard Filling

• 2 cups Fresh rhubarb, chopped (about 1/2 inch pieces)
• 3/4 cup Granulated sugar Adjust based on rhubarb tartness
• 1/4 cup All-purpose flour
• 2 large Eggs Lightly beaten
• 1/2 cup Heavy cream
• 1 teaspoon Vanilla extract

Method

 

Instructions

1. Preheat your oven to 350°F (175°C). Line an 8×8 inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.
2. Prepare the crust: In a medium bowl, combine the flour, sugar, and salt for the crust. Cut in the cold, cubed butter using a pastry blender or your fingers until the mixture resembles coarse crumbs. Press the mixture firmly and evenly into the bottom of the prepared pan.
3. Bake the crust for 15 minutes until lightly golden brown. While the crust bakes, prepare the filling.
4. Prepare the filling: In a separate bowl, gently toss the chopped rhubarb with the 3/4 cup of sugar and the 1/4 cup of flour until the rhubarb is evenly coated. Set aside.
5. In another bowl, whisk together the eggs, heavy cream, and vanilla extract until just combined. Do not overmix.
6. Pour the egg mixture over the partially baked crust. Gently scatter the sugared rhubarb mixture evenly over the top of the custard layer.
7. Return the pan to the oven and bake for an additional 40-45 minutes, or until the custard is set (a slight jiggle in the very center is acceptable) and the edges are lightly browned. A toothpick inserted into the custard should come out mostly clean.
8. Let the bars cool completely in the pan on a wire rack (this is crucial for clean slicing). Once cooled to room temperature, chill in the refrigerator for at least 2 hours before lifting out using the parchment paper overhang and cutting into 12 squares.

Notes

Ensure the rhubarb is chopped into even pieces for consistent baking. Cooling completely before slicing is the key to perfect, neat bars. These store well in the refrigerator for up to 4 days.