Clementine Upside-down Cake

Ingredients

• 4 tbsp unsalted butter
• 0.75 cup light brown sugar
• 6 medium clementines – thinly sliced into 0.25-inch rounds, seeds removed
• 1.5 cups all-purpose flour
• 1 tsp baking powder
• 0.5 tsp baking soda
• 0.5 tsp fine salt
• 8 tbsp unsalted butter – softened
• 0.75 cup granulated sugar
• 2 medium clementines – zested (about 2 tsp) and juiced (2 tbsp reserved)
• 2 large eggs – room temperature
• 1 tsp vanilla extract
• 0.75 cup sour cream – room temperature

Instructions

1. Preheat the oven to 350°F (175°C). Place a 9-inch ovenproof skillet (preferably cast iron) on the stove over medium heat.
2. Make the caramel: Melt 4 tbsp unsalted butter in the skillet, then add the light brown sugar. Cook, stirring, until the mixture is bubbling and smooth, 1–2 minutes.
3. Arrange the clementine slices over the caramel in a tight, overlapping layer to fully cover the bottom. Let them simmer gently until just glossy at the edges, 2–3 minutes. Remove the skillet from the heat.
4. In a bowl, whisk together the all-purpose flour, baking powder, baking soda, and fine salt.
5. In a separate bowl, cream the softened 8 tbsp unsalted butter with the granulated sugar using a hand mixer until pale and fluffy, 2–3 minutes. Beat in the clementine zest from the zested fruit, then beat in the eggs one at a time. Mix in the vanilla extract, sour cream, and 2 tbsp clementine juice until smooth.
6. Add the dry ingredients to the wet and stir just until combined; the batter will be thick.
7. Spoon the batter over the clementines in the skillet and spread gently to the edges without disturbing the fruit.
8. Bake until the top is golden, the edges are bubbly, and a toothpick inserted into the center of the cake portion comes out clean, 35–45 minutes.
9. Cool in the skillet on a rack for 10 minutes. Run a thin knife around the edge, then invert onto a serving plate; replace any fruit that sticks to the pan.
10. Let cool at least 20 minutes before slicing. Serve warm or at room temperature.