3 Ingredient Rhubarb Squares

Simple, sweet, and a little bit tangy — these 3 Ingredient Rhubarb Squares are the ultimate no-fuss dessert. Perfect for spring and early summer, they let the bold flavor of fresh rhubarb shine with the help of just two pantry staples: boxed cake mix and butter. The result? A soft, chewy square with caramelized edges and pockets of tart rhubarb, ready in no time.

If you’re a fan of quick desserts or need something easy for a last-minute gathering, this recipe is a lifesaver. No mixer, no fancy techniques, and minimal cleanup. Just stir, layer, bake, and enjoy!

Why You’ll Love 3 Ingredient Rhubarb Squares

Only three ingredients: Super simple and budget-friendly.
No mixing bowl required: You can mix everything right in the baking dish.
Tart and sweet: Rhubarb pairs beautifully with buttery cake mix.
Perfect for beginners: Great for kids or baking novices.
Ready in under an hour: Quick prep and bake time.
Freezer-friendly: Make a batch and save some for later.

Ingredients You’ll Need

1 box yellow cake mix – White cake mix also works well.
1 cup unsalted butter, melted – Adds richness and helps the crust hold together.
2 ½ cups rhubarb, chopped – Fresh is best; if using frozen, thaw and drain well.

Step-by-Step Instructions

Preheat the oven:
- Set your oven to 350°F (175°C).
- Grease a 9x13-inch baking dish or line with parchment paper.
Prepare the crust:
- Pour the dry cake mix into a large bowl or directly into the prepared baking dish.
- Add the melted butter.
- Stir until a thick, crumbly dough forms.
- Press about two-thirds of the dough evenly into the bottom of the baking dish to form a crust.
Add the rhubarb:
- Scatter the chopped rhubarb evenly over the crust.
- Gently press it into the crust so it bakes in and doesn’t sit loosely on top.
Top with remaining dough:
- Crumble the remaining dough mixture over the rhubarb.
- It doesn’t need to cover every inch — some rhubarb peeking through is fine.
Bake the squares:
- Bake in the preheated oven for 35–40 minutes.
- The top should be lightly golden and the edges bubbly.
Cool completely:
- Let the pan cool fully on a wire rack before slicing.
- Cooling helps the squares firm up for easier cutting.
Slice and serve:
- Cut into squares and serve as-is or with a dollop of whipped cream or scoop of vanilla ice cream.

Serving and Storage Tips

Serve with: Whipped cream, ice cream, or a dusting of powdered sugar.
To store: Keep in an airtight container at room temperature for up to 3 days.
To refrigerate: Store for up to 5 days; reheat slightly before serving.
To freeze: Freeze individually wrapped squares for up to 2 months.

Helpful Notes

Frozen rhubarb tip: If using frozen rhubarb, thaw and pat dry to avoid excess moisture.
Make it your own: Add a sprinkle of cinnamon, nutmeg, or orange zest for extra flavor.
Swap-ins: Try using chopped apples, strawberries, or raspberries for a fruity twist.
Make it crispier: Sprinkle a bit of sugar on top before baking for extra crunch.
Serving idea: Serve warm with cream for a rustic spring dessert.

Frequently Asked Questions

Can I use white cake mix instead of yellow?
Yes, both work well. Yellow adds a richer flavor, while white lets the rhubarb shine.
What if I only have salted butter?
You can use it — just skip any additional salt.
Can I use frozen rhubarb?
Yes, thaw it completely and drain well to prevent soggy bars.
Can I make this gluten-free?
Use a gluten-free cake mix that substitutes 1:1 with regular.
Do I need to cook the rhubarb first?
Nope! It softens beautifully while baking.

Final Thoughts

These 3 Ingredient Rhubarb Squares are proof that you don’t need a long list of ingredients or complicated steps to make something delicious. With the tart zing of rhubarb, the buttery crumble of cake mix, and the convenience of a one-pan dessert, this recipe is destined to become a seasonal favorite.

Perfect for brunch, picnics, or spontaneous baking sessions, these squares bring ease and flavor to your table. Try them once and keep them on repeat — and don’t forget to share your version! 🍰🌸