Preheat the oven to 350°F (175°C). Butter and flour two 9-inch round cake pans. Sift the flour and salt into a large mixing bowl, then whisk in the sugar until well combined.

In a saucepan, combine the water and butter. Heat until the butter has fully melted. Remove from heat and stir in the baking soda, buttermilk, eggs, and vanilla extract until smooth.

Pour the hot butter mixture into the dry ingredients. Stir gently until the batter is smooth and lump-free. Divide the batter evenly between the prepared pans and bake for 20–25 minutes, or until a toothpick inserted in the center comes out clean. Allow to cool in the pans for 15 minutes before transferring to parchment-lined wire racks to cool completely.

Place 2 cups of sugar, the butter, cream, and salt in a large saucepan over medium heat. Cook until the mixture is nearly at a boil. In a separate small saucepan, melt the remaining ½ cup of sugar without stirring, occasionally swirling the pan until the sugar forms a golden syrup. Carefully pour the syrup into the cream mixture.

Continue cooking the frosting mixture until it reaches 232°F (soft-ball stage) on a candy thermometer. Remove from the heat and stir in the vanilla extract. Allow the frosting to cool for 15 minutes.

Using a hand mixer, beat the cooled caramel mixture until it thickens to a spreadable consistency. If it becomes too stiff, add a small amount of cream until the desired texture is reached. Spread the frosting over the cooled cake layers, stack them, and finish covering the top and sides.