Seriously Simple: Nectarines add a taste of summer to an upside-down cake
1 1/2 teaspoons baking powder
1/2 cup (8 tablespoons) unsalted butter, at room temperature
2/3 baking cup sugar
1 1/2 teaspoons vanilla
2 large eggs
1/2 cup sour cream
1 small nectarine, finely chopped
For the nectarines:
6 tablespoons unsalted butter
1/3 cup dark brown sugar
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