This blueberry upside down cake is soft, buttery, with a jammy blueberry topping! It's the perfect dessert, especially when served with a dollop of vanilla ice cream or whipped cream!
Preheat the oven to 325 degrees F. Brush a 9x2 inch cake pan with butter, brushing the entire pan to ensure all of it is coated. Line the bottom and sides of the pan with parchment paper. Set aside.
Rinse off blueberries and pat them dry with a paper towel, removing as much moisture as possible.
Now make the cake batter. Combine cake flour, baking powder, nutmeg, and kosher salt in a large bowl and whisk together. Set aside.
In a separate bowl, combine room temperature butter, oil, lemon zest, and sugar. Use an electric hand mixer to beat together for 2 minutes, until fully combined and pale in color. Add in the eggs, egg yolk, and vanilla extract. Continue to mix for about 1 minute, until combined.
Add half of the dry ingredients and mix. Pour in the buttermilk and mix until combined, about 10 seconds. Then, add the remainder of the flour mixture and continue to mix until a smooth batter forms, about 15 seconds.
Pour melted butter onto the bottom of the cake pan and sprinkle brown sugar on top. Add the blueberries on top of the sugar/butter mixture, then gently pour the batter on top of the blueberries. Smooth batter into an even layer, ensuring all of the blueberries are covered.
Bake for 55-65 minutes, until a toothpick inserted into the center of the cake comes out with just a few moist crumbs. Allow the cake to cool in the pan for 8-10 minutes.
Use a butter knife to gently slide between the pan and the cake, then invert cake onto a wire rack. (there will be syrup that drips down, to prevent a mess, place the cooling rack onto a baking sheet to catch any drippage)
Serve with vanilla ice cream or whipped cream while still warm!
Notes
After baking, let the cake cool in the pan for at least 8 minutes before inverting. This is crucial so that the cake doesn't fall apart when inverting. It also helps the fruit layer to set and not fall apart when you flip it over.
Use room temperature ingredients!
If the cake has domed in the center while baking, use a knife to flatten the top. This cake is baked at 325 degrees F instead of 350 for a more even, flat topped cake. However, if your oven runs hot, the cake will likely rise in the center. Make sure to cut off the domed top before inverting to prevent the cake from falling apart.
Use a kitchen scale to measure out the ingredients. This will allow for the most precise measurements, ensuring the success of the recipe. I highly recommend using digital scales in all baking recipes!