Preheat oven to 325 degrees F. Line standard size muffin tin with cupcake liners Combine flour, baking powder, and salt in a medium bowl and set aside. In bowl of a stand mixer using a paddle attachment; cream butter and brown sugar on medium-high speed for about 3 minutes until pale and fluffy. Add eggs one at a time scraping down the sides between each addition. Mix in the vanilla. Add the flour mixture in 3 batches alternating with the buttermilk and beat until incorporated. Use 1/4 measuring cup to scoop batter into muffin tins. Bake for 20 minutes or until toothpick inserted comes out clean. Cool 10 minutes then remove cupcakes to cooling rack to cool completely.

In a medium sauce pan over medium-high heat dissolve sugar whisking occasionally. Cook until sugar turns a deep amber. ( can easily burn so watch closely!) Stir in butter until melted. Carefully add a small amount of heavy cream stirring constantly. It will bubble up. Continue to add cream until all incorporated. Whisk until smooth. Remove from heat and cool.

In a medium sauce pan stir sugar and water together over medium high heat. bring to a boil and cook without stirring until it turns a deep amber. Remove from heat and add heavy cream and vanilla. Stir until smooth. Set aside and let cool for about 20 minutes. In bowl of stand mixer with paddle attachment beat butter on medium high until light in fluffy (about 3 min.) Reduce speed to low and gradually add confectioner sugar and sea salt. Scrape sides of bowl and mix until incorporated. Continue mixing on low speed and pour cooled caramel in to combine. Increase speed and beat for about 3 minutes until light and fluffy.

Using the large open end of a pastry tip cut out a small circle in center of each cupcake. Pour caramel into each center.

Fill pastry bag with buttercream fitted with your choice of tip and frost cupcakes.