Ingredients
Equipment
Method
Make the Blueberry Reduction
- Add 350g (2½ cups) frozen blueberries, 75g (⅓ cup) granulated sugar, 2 tsp lemon juice, and a pinch of salt to a medium saucepan.
- Cook over medium heat until the berries release their juices and begin bubbling, about 5–10 minutes.
- Mash the berries well with a spoon or potato masher.
- Reduce the heat to medium-low and simmer uncovered, stirring every 5 minutes, until the mixture reduces to approximately 275g.
- The reduction should be thicker than a sauce but thinner than jam.
- Cool completely.
- Divide the reduction into:
- 100g (about ⅓ cup) for the cake base
- 75g (about ¼ cup) for swirling
- 100g (about ⅓ cup) for the sauce
Make the Blueberry Lemon Cake Base
- Preheat the oven to 325°F (163°C). Line an 8×8-inch metal baking pan with parchment paper.
- In a large bowl, whisk together 85g (6 tbsp) melted butter, 115g (½ cup + 1 tbsp) sugar, and 1 tbsp lemon zest.
- Whisk in 1 large egg and 1 tsp vanilla extract.
- Add 90g (¾ cup) all-purpose flour, ¾ tsp baking powder, and ¼ tsp kosher salt and stir until combined.
- Stir in 45g (3 tbsp) milk and 100g (about ⅓ cup) blueberry reduction until smooth.
- Spread evenly into the prepared pan.
Par-Bake the Base
- Bake the cake base for 18 minutes.
- The center should no longer look raw but should not be fully baked.
Make the Gooey Butter Layer
- In a medium bowl, whisk together 140g (10 tbsp) melted butter and 165g (¾ cup + 1 tbsp) sugar.
- Add 2 large eggs, 1 large egg yolk, and 2 tsp vanilla extract and whisk until smooth.
- Whisk in 90g (¾ cup) powdered sugar, 45g (⅜ cup) flour, and ¼ tsp kosher salt.
- Stir in 90g (6 tbsp) heavy cream until fully combined.
Assemble
- Remove the partially baked cake base from the oven.
- Carefully pour the gooey butter layer over the base.
- Dollop 75g (about ¼ cup) blueberry reduction across the surface.
- Use a knife to gently swirl the reduction through the gooey layer, keeping most of the swirl in the top layer.
Bake
- Return the pan to the oven and bake for 42–48 minutes.
- The cake is done when:
- The edges are set.
- The top no longer appears wet.
- The center wobbles slightly but does not slosh.
Cool
- Allow the cake to cool for 30 minutes before serving.
- Make the Blueberry Butter Sauce
- Add 100g (about ⅓ cup) blueberry reduction, 1 tbsp butter, 1–2 tbsp heavy cream, and a pinch of salt to a small saucepan.
- Warm over low heat until glossy and pourable.
Serve
- Serve warm with vanilla ice cream.
- Spoon the warm blueberry butter sauce over the top.
Notes
- Frozen blueberries provide the most consistent flavor and color.
- Reducing the blueberries to approximately 275g concentrates the flavor without making the mixture too thick.
- The blueberry reduction can be made up to 3 days ahead, making assembly even easier.
- An 8×8-inch metal pan creates the ideal gooey texture and thickness.
- For the best experience, serve warm with vanilla ice cream and blueberry butter sauce.
