Place sugar in a medium saucepan over medium heat. Swirl the pan gently as the sugar begins to melt and turn golden, about 4 minutes, until you have a deep amber liquid.

Remove from heat and slowly pour in the coconut milk while whisking constantly. The mixture will bubble up, then smooth out as you whisk.

Return to low heat and simmer the sauce for 3 minutes, whisking often, until it just coats the back of a spoon.

Remove from heat, stir in the vanilla extract and sea salt, then pour into a clean jar while warm. Let cool before storing.