Blueberry-Lime Buttermilk Upside Down Cake

I came up with this cake to use up little bits of things I had laying around: blueberries, white chocolate, buttermilk and limes. And I gotta say, I love this cake. A hint of buttermilk and white chocolate in the light cake with a crispy crusty "bottom", enriched with an sweet and sticky brown sugar-blueberry-lime "top." If you are not a huge fan of very sweet desserts, you may want to reduce the brown sugar in the topping to 1/2 cup or so. It is phenomenal served with a scoop of homemade vanilla ice cream!

• Ready In: 1 hr 20 mins
• Serves: 10

Ingredients

• 4  tablespoons unsalted butter, cut into 4 pieces
• 2⁄3 cup light brown sugar, tightly packed
• 2  cups fresh blueberries
• 2  teaspoons lime zest, grated
• 1 1⁄3 cups all-purpose flour
• 1 1⁄2 teaspoons double-acting baking powder
• 1  pinch salt
• 1⁄2 cup unsalted butter, softened
• 1  cup sugar
• 2  large eggs, at room temperature
• 1 1⁄2 teaspoons pure vanilla extract
• 1⁄2 cup buttermilk (or sour milk-I have used sour milk made with 1/2 t lime juice for extra lime flavor)
• 1⁄2 teaspoon baking soda
• 2  ounces white chocolate, coarsely chopped

Directions

1. Preheat the oven to 350 degrees F.
2. In a 9 inch cast iron skillet, melt the butter over low heat. Stir in the brown sugar and cook, stirring, until the mixture is smooth and bubbling, about 3-4 minutes. Remove the pan from the heat and arrange the blueberries evenly over the brown sugar mixture. Scatter the lime zest over the blueberries.
3. .
4. Sift the flour, baking powder and salt together in a small bowl, set aside. Mix buttermilk with baking soda and stir to combine (may foam up), set aside.
5. In a large bowl, beat the butter until creamy using a medium speed on your mixer, about 30 seconds. Add the sugar and continue to beat until the mixture is light in texture, about 2-3 minutes.
6. Beat in the eggs, one at a time. Beat in the vanilla and white chocolate.
7. On low speed, beat in half the flour mixture until just combined. Scrape down the bowl and beat in the buttermilk. Beat in the remaining flour mixture until just combined.
8. Spoon batter over the topping in the cake pan, spreading it evenly over the berries until they are completely covered.
9. Bake until a toothpick inserted into the center of the cake comes out clean, 45-50 minutes. Cool in the pan on a wire rack for about 5 minutes.
10. Run a knife around the edge of the cake to release it from the sides of the pan. Invert a serving plate over the cake and turn the cake out onto the plate.
11. Let cool 30 minutes before serving plain or with a scoop of vanilla ice cream.