1. Preheat oven to 350 degrees F (175 degrees C). Grease and flour two 8″ or 9″ inch round cake pans.
2. In a medium bowl or stand mixer, cream together the sugar and butter until light and fluffy, about 3-4 minutes. Beat in the eggs one at a time, making sure each is completely incorporated before adding the next, then stir in the vanilla. Combine flour, salt and baking powder in a separate bowl. Fold into the batter until completely combined. Stir in the milk until batter is smooth. Pour batter equally into the prepared pans.
3. Bake for 30 to 40 minutes in the preheated oven. Cake is done when it springs back to the touch.

For the buttercream

1. In the bowl of a stand mixer fitted with the paddle attachment, whip butter for 8 minutes. Butter will become very pale & creamy.
2. Add remaining ingredients except caramel and mix on low speed for 1 minute, then on medium for 4 minutes. Frosting will be very light, creamy and fluffy. Add the caramel and mix for another 2 minutes.
3. Best used right away (for ideal spreading consistency).

For assembly

1. Place a small dollop of frosting in the center of your serving plate or a cake board, and place the bottom cake layer on top.
2. Spread the reserved 1/4 cup of caramel over the top of the cake layer. Spread 1 cup of frosting on top of the caramel and spread evenly.
3. Place 2nd cake layer face-down on top. Place a generous scoop of frosting on top, and frost however desired! For this cake, I just dolloped the frosting around and swirled it with the edge of a rubber spatula. Feel free to frost however you like best.
4. If desired, drizzle caramel over the top of the frosted cake. Keep refrigerated until serving.