Combine sugar and water in a medium saucepan. Cook over medium heat until the sugar is completely dissolved, using a wet pastry brush to remove any sugar crystals that form at the edge of the mixture.

Increase heat to medium-high and cook without stirring until the mixture turns medium amber. Immediately remove the pan from heat and pour in 2 2/3 cups of heavy cream.

Whisk until the sauce is smooth. If lumps occur, place the caramel over medium heat and stir until they dissolve.

Add butter and stir until melted. Whisk in the vanilla extract and fine grain sea salt.

Pour the caramel sauce into a medium microwave-safe bowl or into a fondue pot with an active burner.

Just before serving, drizzle the remaining 2 tablespoons of heavy cream on top of the caramel and swirl using a fork.

Gently sprinkle a pinch of flake sea salt on the surface of the fondue. Arrange fruits and cake pieces around the pot for dipping.

If using a fondue pot with a burner, regulate the heat to keep the fondue warm, not hot. If using a bowl, re-heat caramel as needed in the microwave in 30-second increments.