In a heavy-bottomed saucepan or Dutch oven, whisk together the coconut milk, sugar, and baking soda until combined.

Place the pot over medium-high heat and bring the mixture to a gentle boil, stirring frequently to ensure the sugar dissolves completely.

Reduce the heat to low to maintain a steady simmer. Cook for 45 to 55 minutes, stirring occasionally to prevent the bottom from burning.

As the mixture cooks, it will darken to a deep caramel color and thicken significantly. It is ready when it coats the back of a spoon and leaves a trail when you run your finger through it.

Remove from heat and stir in the vanilla extract and sea salt. Let the mixture cool completely in the pan or transfer to a glass jar; it will continue to thicken as it cools.