My cousin brought this to our pool day and it was gone instantly. Only 3 ingredients to make the most perfectly tart and sweet weekend dessert.

This slow cooker 3-ingredient blue lagoon dump cake is the kind of easy, cheerful dessert that disappears the minute you set it down by the pool. My cousin first brought this to a family pool day, lined the slow cooker with foil, dumped everything in, and by the time we’d all dried off, there was nothing but a blue-stained spoon left. The bright, almost neon blue citrus filling bubbles up through a buttery golden cake mix crust, giving you that tart-sweet bite that feels like a summer cocktail turned into a warm, spoonable treat. It’s pure Midwestern potluck magic: simple pantry ingredients, no fuss, and a slow cooker doing all the work while you enjoy the weekend.

Serve this blue lagoon dump cake warm right from the slow cooker, scooped up with a big spoon and piled into bowls. A scoop of vanilla ice cream or a dollop of whipped topping melts into the hot, sticky blue filling and buttery crust in the nicest way. It’s perfect with grilled burgers, brats, or fried chicken—just the kind of sweet finish you want after a salty, smoky cookout. A pitcher of lemonade or sweet tea on the side keeps the tart, citrusy theme going. If you’re taking it to a pool day or picnic, keep the slow cooker on warm so folks can wander by, lift the lid, and help themselves.

Servings: 8-10

1 (21-ounce) can blue raspberry or blue raspberry-lemon pie filling (or blue citrus dessert filling)

Line the inside of a 5- to 6-quart slow cooker with heavy-duty aluminum foil, pressing it up the sides to make a sling. This helps the cake lift out easily and keeps the edges from overbrowning.

Lightly coat the foil with nonstick cooking spray or a thin layer of butter so the crust releases cleanly after cooking.

Open the can of blue raspberry or blue citrus pie filling and pour it into the bottom of the foil-lined slow cooker. Spread it into an even layer so the entire bottom is covered. The filling should look like a bright, neon blue pool at the base.

Sprinkle the dry yellow cake mix evenly over the blue filling. Do not stir. Use clean, dry fingers or the back of a spoon to gently level the cake mix so it covers all the filling in a fairly even layer.

Slowly drizzle the melted butter evenly over the dry cake mix, trying to moisten as much of the surface as possible. It’s fine if a few dry spots remain; they’ll turn into a crisp, buttery topping as it cooks.

Place a layer of paper towels over the top of the slow cooker (without touching the batter), then set the lid on top. This helps catch condensation so the crust bakes up soft and buttery instead of soggy.

Cook on HIGH for 2 to 2 1/2 hours, or on LOW for 3 1/2 to 4 hours, until the top is mostly set, the edges are golden, and the blue filling is bubbling up around the sides and through little cracks in the crust. The center may still look a bit soft and sticky—that’s what you want for a moist dump cake.

Turn the slow cooker to WARM and let the cake rest, uncovered, for about 15–20 minutes. This helps the filling thicken slightly while staying gooey and lets the crust firm just enough to scoop cleanly.

Use the foil sling to carefully lift the cake out onto a rimmed baking sheet if you’d like that bubbling, blue-on-golden look for serving or photos, or simply scoop straight from the slow cooker into bowls. Serve warm, with ice cream or whipped topping if you like.

Re-cover and keep on WARM for serving at a party or pool day, up to 2 hours. Refrigerate any leftovers within 2 hours of cooking, covered, and reheat gently in the microwave before serving.

For a slightly more citrusy punch, you can use a lemon cake mix instead of yellow, though yellow keeps that classic buttery Midwestern dump cake flavor. If you can’t find blue raspberry or blue citrus pie filling, look for a blue dessert topping or filling intended for pastries; the key is a thick, spoonable, neon-blue fruit or citrus base so you get that lagoon look when it bubbles up through the crust. You can also tuck a few thin lemon slices on top of the filling before adding the cake mix for extra tartness and a pretty accent. For a smaller crowd, halve the recipe and use a 3- to 4-quart slow cooker, checking for doneness about 30 minutes earlier. Food safety tips: Always cook this dessert on HIGH or LOW as directed, with the lid on, so it reaches a safe, steamy temperature throughout. Do not leave the slow cooker on WARM for more than 2 hours after cooking; any leftovers should be cooled slightly, then refrigerated promptly in a shallow container. Reheat leftovers until piping hot in the center before serving. Avoid using dented or bulging cans of filling, and discard any product that smells off or has an unusual color or texture beyond the intended bright blue.