Keto Strawberry Rhubarb Dump Cake (The Crispy Topping Method)

Imagine sinking your spoon into a warm, bubbling layer of jammy strawberries and tart rhubarb, topped with a buttery, golden-brown crust that literally melts in your mouth—all without a single grain of sugar. If you’re a busy mom like me, you need a dessert that feels like an indulgence but doesn’t require hours of effort or a messy kitchen.

This Keto Strawberry Rhubarb Dump Cake is your answer. Forget dry, gritty keto desserts that taste like sadness. This is the ultimate “dump and bake” miracle that uses a few smart tricks to deliver a rich, comforting dessert that’s perfectly low-carb. It’s time to enjoy dessert again, guilt-free.

At-A-Glance

• Dietary: Keto, Gluten-Free, Sugar-Free
• Time: 45 minutes
• Difficulty: Very Easy
• Cost per serving: $1.85

Why This Recipe Works (The “Crispy Lid” Method)

Most keto dump cakes fail in two ways: the fruit turns into a watery soup, and the almond flour topping becomes a gummy paste. This recipe uses the “Crispy Lid” Method to solve both problems.

First, we create a Jammy Fruit Base. By tossing the fruit with a tiny pinch of xanthan gum, we help the natural juices thicken into a beautiful syrup as it bakes. This prevents the dreaded watery puddle at the bottom of the dish.

Second, we build a Butter Barrier. Instead of mixing the butter in, we lay thin, cold slices over the entire surface of the dry cake mix. As the butter melts downwards, it slowly fries the almond flour, creating a distinct, crispy, shortbread-like topping that is completely separate from the fruit layer. It’s the secret to a perfect texture every single time.

Key Ingredients & Notes

• 2 cups Fresh Strawberries & 2 cups Fresh Rhubarb, chopped: Chef’s Tip: If using frozen, thaw and drain them on a paper towel first to remove excess water.
• 1/4 tsp Xanthan Gum: Our secret weapon! This tiny amount is all you need to create a jammy, non-watery filling. Do not skip this.
• 1 package (11oz) King Arthur Keto Yellow Cake Mix: This is my preferred brand because it uses almond flour and doesn’t have a strange aftertaste. Any high-quality almond-flour based keto cake mix will work.
• 1/2 cup (115g) Salted Butter, chilled and thinly sliced: Using cold, salted butter is crucial. The salt enhances the fruit flavor and cuts the “cooling” sensation of some keto sweeteners.

Equipment Needed

• 9×9 Inch Square Metal Baking Pan (metal gives you the best crust)
• Sharp knife and cutting board
• Small bowl

Step-by-Step Instructions

Step 1: Prep the Oven and Pan. Preheat your oven to 350°F (175°C). Lightly grease your baking dish.

Step 2: Create the Jammy Filling. In a bowl, toss the sliced strawberries and chopped rhubarb with the xanthan gum until lightly coated. Dump this fruit mixture into the bottom of your prepared dish and spread it evenly.

Step 3: Add the Topping. Open the bag of keto cake mix and sprinkle the dry mix evenly over the top of the fruit. Gently shake the pan to level it out.

Step 4: Build the “Crispy Lid.” Arrange the thin slices of cold butter across the entire surface of the dry mix, covering as much as possible like a mosaic. The more coverage, the crispier your topping will be.

Step 5: Bake. Bake for 35-40 minutes, until the fruit is bubbling vigorously around the edges and the top is golden brown. Let it cool for at least 10 minutes before serving. This allows the fruit filling to set up properly. Serve warm, perhaps with a scoop of keto vanilla ice cream or a dollop of my 2-Minute Keto Whipped Cream.

Expert Tips

• No Dry Spots Allowed: Halfway through baking, peek at the topping. If you see any dry, powdery spots of flour, place a tiny sliver of extra butter on top to help it brown.
• Get the Ratios Right: Don’t be tempted to add more fruit than the recipe calls for. Too much fruit will release too much water and can overwhelm the topping, leading to a soggy result.

Variations / Substitutions

If you don’t have rhubarb, this recipe is fantastic with a mix of blueberries and raspberries instead. For a dairy-free version, you can substitute the butter with chilled, solidified coconut oil, but the browning will be less even.

FAQ

Why is my keto dump cake gummy instead of crispy?
This almost always happens when melted butter is used instead of cold, sliced butter. Melting the butter first creates a paste with the almond flour. The “Crispy Lid” method of melting from the top down is essential for a shortbread texture.

Can I make my own keto “cake mix” topping?
Yes! A simple mix is 1.5 cups almond flour, 1/2 cup granulated keto sweetener (like Lakanto), 2 tsp baking powder, and a pinch of salt. Sprinkle this over the fruit just like the boxed mix.

How should I store leftovers?
Cover and store in the refrigerator for up to 4 days. Unlike traditional cakes, the almond flour topping stays surprisingly crisp, and many people love eating it cold!