While the cake is baking, you can prepare the optional caramel drizzle.
Add the sugar and water to a pan or sauce pot. Put the pan on medium heat and give the mixture a swirl. Let it heat up, undisturbed, until the sugar is fully melted and the mixture is bubbling slightly. This will take about 4-5 minutes.
Use a spatula to brush down the edges and then allow the sugar to continue to cook, undisturbed, until it starts to turn slightly golden like honey.
Then whisk in the butter one small piece at a time, stirring to combine.
When the butter is fully combined, remove the pan from the heat and pour in the cream. Continue whisking quickly until a thick caramel forms.
Whisk in the salt and pour into a bowl to cool for 5-10 minutes. You can use this on the cake, and of course store any leftovers in a jar for later!