Cupcakes
1 ½ cups all-purpose flour
1 teaspoon baking powder
¼ teaspoon kosher salt
1 stick unsalted butter, room temperature
1 cup plus 2 tablespoons packed light brown sugar
2 large eggs, room temperature (20-30 mins out of refrigerator)
2 teaspoons pure vanilla extract
½ cup plus 2 tablespoons buttermilk, room temperature (20-30 mins out of refrigerator)
Filling
About ½ cup Caramel Sauce
Frosting
1 ½ cups granulated sugar
½ cup water
6 large egg whites, room temperature (15-20 minutes out of refrigerator)
¾ teaspoon cream of tartar
4 sticks unsalted butter, room temperature
2 teaspoons pure vanilla extract
¼ cup Caramel Sauce
1 teaspoon Maldon Sea Salt, for topping