Cover the slow cooker with the lid and cook on HIGH for 2 to 2 1/2 hours, or on LOW for 3 1/2 to 4 hours, until the blueberries are bubbling around the edges and the cake mix on top looks set and mostly cooked through. The center may be a little softer and more spoon-cake-like, which is perfect for this style of dessert.
Turn off the slow cooker and let the dump cake sit, covered, for about 10 to 15 minutes to thicken slightly. This rest time helps the hot fruit settle and makes it easier to scoop.
Spoon the warm lemon blueberry dump cake into bowls and serve as is, or top with vanilla ice cream, whipped cream, or yogurt. Store any leftovers, cooled to room temperature, in a covered container in the refrigerator for up to 3 days. Reheat gently in the microwave or on the warm setting of the slow cooker.
Variations & Tips
For picky eaters who are unsure about berries, you can reduce the blueberries to 3 cups and add 1 cup of frozen sliced peaches or chopped frozen strawberries to mellow the flavor a bit. If your family prefers things less sweet, cut the granulated sugar down to 1/3 cup or even 1/4 cup; the cake mix already has sugar, so it will still taste like dessert. For a little extra brightness, stir 1 teaspoon of lemon zest into the dry cake mix before dumping it over the berries, or squeeze a tablespoon of lemon juice over the berries before adding the sugar. If you only have salted butter, you can use it—just skip adding any extra salt.
To make this feel more like a breakfast treat for a weekend, serve it with vanilla yogurt instead of ice cream and sprinkle a handful of granola on top for crunch. Food safety tips: Always start with frozen berries straight from the freezer; don’t let them sit out too long before cooking to avoid excess thawing and juice, which can change the texture. Make sure the dessert reaches a bubbling, hot stage around the edges so the center warms through properly. Once cooked, do not leave the dump cake on the warm setting for more than 2 hours; after that, transfer leftovers to shallow containers and refrigerate promptly to keep them safe. Reheat individual portions until steaming hot before serving again.
If you’re cooking for anyone with allergies, double-check the cake mix label for potential allergens like wheat, milk, soy, or eggs, and choose a mix that fits your family’s needs.
