Preheat oven to 325 degrees F, and boil a large pot of water.
Whisk together egg yolks, coconut sugar, vanilla extract, and lemon zest in a large bowl and set aside.
Combine coconut milk and sea salt in a saucepan and heat over medium heat for about 5 minutes, stirring occasionally. Do not bring to a boil.
SLOWLY pour the coconut milk mixture over the egg yolk mixture while whisking constantly.
Strain this mixture through a fine mesh strainer and use a back of a spoon to press down on the lemon zest to get all the liquid out.
Place 4 8-oz ramekins in a baking pan, and pour the strained mixture into the ramekins.
Pour enough boiling water into the baking pan to come halfway up the sides of the ramekins.
Bake for about 35-45 minutes until the custards are set (firm on the edges but slightly jiggly in the center).
Remove from the oven and use a tong to transfer to a cooling rack.
Cool for 1 hour, then cover with a plastic wrap.
Chill for at least 4 hours to overnight.
Sprinkle 1 tsp of coconut sugar over each custard. Use a blowtorch, or place under a broiler* for 4-5 minutes until the top is bubbly and caramelized.
Let it sit for 5 minutes. Serve topped with fruits, if desired.