Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.
Add the buttermilk, vegetable oil, eggs, and vanilla extract to the dry ingredients and mix until well combined.
Carefully add the boiling water to the batter and mix until smooth. The batter will be thin.
Pour the batter into the prepared muffin tin, filling each liner about ⅔ full.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool completely before frosting.
For the frosting, beat the softened butter in a large bowl until creamy.
Gradually add the powdered sugar, caramel sauce, and sea salt, beating until smooth and fluffy. Add heavy cream as needed to reach the desired consistency.
Frost the cooled cupcakes with the salted caramel frosting and enjoy!