Preheat the oven to 350°F (175°C). Grease and line three 9-inch round cake pans with parchment paper. Cream butter and sugar until light and fluffy. Beat in eggs one at a time. Alternate adding sifted flour and buttermilk, beginning and ending with flour. Stir in vanilla extract. Divide batter evenly between prepared pans. Bake for 25–30 minutes or until a toothpick inserted in the center comes out clean. Cool cakes in pans for 10 minutes, then transfer to wire racks to cool completely.

In a medium saucepan, melt butter over medium heat. Stir in brown sugar and cook for 2 minutes. Gradually add evaporated milk, stirring constantly. Bring to a gentle boil and cook for 5 minutes until smooth. Let cool for 10 minutes, then transfer to a mixing bowl. Beat in powdered sugar, one cup at a time, until creamy and spreadable. Stir in vanilla extract.

Place one cake layer on a serving plate. Spread caramel icing evenly over the top. Repeat with the second and third layers. Spread icing over the sides of the cake, smoothing with an offset spatula. Work quickly as the icing sets as it cools.

Optional: Garnish with a pinch of sea salt or pipe extra icing for decoration. Slice and serve. Store leftovers in an airtight container at room temperature for up to 3 days.