Ultimate Rhubarb Cake with Marshmallows and Jello

Finding dessert recipes that bring back childhood memories while still feeling fresh and fun can be tricky. Between busy schedules and picky eaters at the dinner table, sometimes you just want something that’s both nostalgic and guaranteed to get everyone excited about dessert time.

That’s where this rhubarb cake with marshmallows and jello comes in – it’s a cheerful mix of tangy and sweet, super easy to put together, and has that perfect comfort-food feeling that makes everyone smile. Plus, it’s the kind of recipe that works just as well for a casual family dinner as it does for your next neighborhood potluck.

What Kind of Rhubarb Should I Use?

Fresh rhubarb is the way to go for this cake, and you’ll want to look for stalks that are firm and crisp with a bright pink to red color. While you might find both hothouse and field-grown rhubarb at the store, either type works well in this recipe – hothouse tends to be a prettier pink, while field-grown can have a more intense flavor. If fresh rhubarb isn’t in season, frozen rhubarb will work just fine – just thaw and drain it well before using to prevent excess moisture in your cake. When prepping your rhubarb, remember to remove all the leaves (they’re not edible!) and cut the stalks into even-sized pieces so they cook uniformly in the cake.

Options for Substitutions

This fun, nostalgic cake recipe can be tweaked in several ways if you need to make substitutions:

• Rhubarb: If fresh rhubarb isn’t in season, frozen rhubarb works just as well – just thaw and drain it first. In a pinch, you could use strawberries or tart apples, though this will give you a different flavor profile.
• Strawberry gelatin: Feel free to experiment with different Jello flavors – raspberry or cherry work great with rhubarb. Sugar-free gelatin can also be used if you’re watching your sugar intake.
• Mini marshmallows: Regular marshmallows cut into quarters will work, or you can use marshmallow creme (about 2 cups). For a vegan option, try vegan marshmallows.
• White cake mix: Yellow cake mix works just fine here. If you prefer homemade, use your favorite vanilla cake recipe that yields one 9×13 cake.
• Vegetable oil: Any neutral oil works well – canola, coconut (melted), or even melted butter can be used in equal amounts.
• Eggs: For each egg, you can substitute 1/4 cup unsweetened applesauce or one mashed banana. Just note that these might add a slight flavor to your cake.

Watch Out for These Mistakes While Baking

The biggest challenge when working with rhubarb is not preparing it correctly – make sure to trim away all leaves (they’re toxic!) and cut the stalks into even, small pieces (about 1/2 inch) so they cook uniformly and become tender.

A common mistake is skipping the sugar coating step for the rhubarb – tossing the chopped rhubarb with the gelatin powder and sugar before adding it to the pan helps balance its natural tartness and ensures even distribution of sweetness throughout the cake.

When adding the marshmallows, resist the urge to mix them into the cake batter; they should be sprinkled on top, as mixing them in will create gooey pockets that prevent the cake from baking properly.

For the best texture, don’t overbake this cake – pull it out of the oven when a toothpick inserted in the center comes out with just a few moist crumbs (not wet batter), as the residual heat will continue cooking the cake while it cools.

What to Serve With Rhubarb Cake?

This sweet and tangy rhubarb cake is perfect with a scoop of vanilla ice cream, which melts slightly into all those wonderful marshmallow-filled layers. A dollop of freshly whipped cream works great too, especially since it complements the strawberry jello flavors in the cake. If you’re serving this for afternoon tea or coffee, try pairing it with a cup of Earl Grey or a creamy latte – the slight bitterness of the coffee creates a nice balance with the cake’s sweetness. For an extra special touch, you could add some fresh strawberry slices on the side to echo the strawberry jello flavors in the cake.

Storage Instructions

Keep Fresh: This rhubarb cake stays moist and yummy when kept in an airtight container in the fridge. It’ll be good for about 4-5 days, though the marshmallow topping might get a bit softer over time. I like to cover it with plastic wrap first, then put the lid on to keep it extra fresh.

Freeze: While you can freeze this cake, keep in mind that the texture of the marshmallows might change a bit when thawed. If you want to freeze it anyway, wrap individual portions in plastic wrap and aluminum foil, then pop them in a freezer bag for up to 2 months.

Serve Later: When you’re ready to enjoy a piece from the fridge, let it sit at room temperature for about 20 minutes – this brings out the best flavor and texture. The jello and marshmallow layers make this cake quite special, so it’s best enjoyed within the first couple of days when everything is at its freshest.

Preparation Time	15-20 minutes
Cooking Time	50-55 minutes
Total Time	65-75 minutes
Level of Difficulty	Medium

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 3000-3500
• Protein: 40-50 g
• Fat: 150-180 g
• Carbohydrates: 450-500 g

Ingredients

For the rhubarb base:

• 4 cups miniature marshmallows
• 6 cups chopped rhubarb
• 3/4 cup sugar
• 1 packet (3 oz) strawberry gelatin

For the cake:

• 1 box white cake mix (I use Duncan Hines Moist Deluxe)
• 1/2 cup vegetable oil
• 3 eggs (room temperature for better emulsification)
• 1 cup water

Step 1: Prepare the Baking Dish

Spray a 9×13 baking dish with nonstick cooking spray, or line it with parchment paper or aluminum foil.

If using foil, spray it with nonstick cooking spray as well.

Using parchment paper or aluminum foil can make it easier to flip the cake upside down later.

Preheat your oven to 350℉ (175℃).

Step 2: Assemble the Rhubarb Mixture

Dice the rhubarb into about 1/2 inch pieces.

Spread the diced rhubarb and marshmallows evenly across the bottom of the prepared baking dish.

Sprinkle the dry Jello and sugar over the rhubarb mixture.

Use a rubber spatula to gently mix the ingredients together without disturbing the parchment or foil lining.

Step 3: Prepare and Add Cake Mix

Prepare the cake mix according to the package instructions in a separate bowl.

Once prepared, pour the cake batter evenly over the rhubarb mixture in the baking dish.

Make sure not to stir the layers together; the batter should sit on top of the rhubarb mixture.

Step 4: Bake the Cake

Place the assembled dish in the preheated oven and bake for 50-55 minutes, or until a toothpick inserted into the center of the cake comes out clean.

This indicates that the cake is fully cooked through.

Step 5: Flip and Serve the Cake

Once baked, you can cool the cake in the pan and flip individual pieces upside down when serving to achieve the upside-down effect.

Alternatively, as soon as the cake has finished baking, run a knife around the edges to loosen it.

Set a heatproof plate or serving dish face-down on top of the baking dish, and carefully invert the cake onto the serving dish.

Leave the baking dish inverted over the plate for a minute to allow any extra strawberry custard to drizzle over the cake.

Then, remove the baking dish.

Step 6: Serve and Store

Allow the cake to cool completely before serving.

Top with whipped cream for added flavor and presentation.

Store any leftovers in the refrigerator to keep the cake fresh.