Wash and slice nectarines, leaving the skins on. Set aside.
In a mixing bowl, add the batter ingredients and whisk to combine. Let rest. The batter will rise and be light and fluffy.
Preheat the oven to 350°F. In a 10-inch cast iron skillet, melt butter over medium-high heat. Use a rubber spatula or wooden spoon to stir butter as it begins to get frothy. As the butter browns, you'll smell a nutty aroma. Continuously stir until the butter is a light to a golden brown color similar to a caramel color. This is a bit hard to see in the black cast iron skillet, but I was able to tell how golden the color was when using a white rubber spatula.
Once the butter is browned, pour the batter on top. Do not stir. Gently place the sliced nectarines on top of the batter. Sprinkle with coarse turbinado sugar.
Bake the cobbler in the oven at 350°F for about 50-60 minutes. The edges will look crispy and very golden. Make sure the center of the cobbler is cooked before removing it from the oven.
Let cool for at least 10 minutes before serving. Serve with vanilla ice cream or fresh whipped cream.
If you don't have a cast iron skillet, bake cobbler in an 11x7 inch glass baking dish or a 9" round pie dish.
You can substitute fresh or canned peaches for the nectarines.
If using unsalted butter, add 1/4 teaspoon salt.
Keywords: nectarine cobbler, peach cobbler, brown butter cobbler, cast iron skillet cobbler