Preheat the oven to 300 (F). Place 4 cups heavy cream in a medium, heavy-bottomed saucepan; scrape in seeds from the vanilla bean and add pod. Bring to a boil over medium heat. Remove from heat and set aside, discarding the vanilla bean pod.
Combine 3/4 cup plus 2 tablespoons granulated sugar and 2 tablespoons water in a large, heavy-bottomed saucepan. Bring to boil over medium-high heat, using a heatproof rubber spatula to dissolve sugar. Continue boiling until the mixture turns the amber color of your choice (see baker's notes), swirling the pan occasionally and using a heatproof rubber spatula to brush down the sides of the pan.
Once the mixture is the color of your choice, remove from heat. Slowly stream in the warm cream (from the 1st step) to the caramel, stirring constantly until smooth. At first the mixture will bubble vigorously, but it will calm down and lighten.
In a large, heatproof bowl, whisk together 6 large egg yolks, remaining 2 tablespoons granulated sugar, zest from one medium orange and 1/8 teaspoon kosher salt until well combined. Slowly stream in caramel, whisking constantly until the mixture is a uniform color.
Divide custard among 8 ramekins and place in a large baking dish or roasting pan. Fill the pan with boiling water until water reaches at least halfway up the sides of the ramekins. Bake until the custard is just set but jiggly in the center, around 60 - 70 minutes. BE CAREFUL NOT TO OVERBAKE — the custards will continue to set outside the oven. Remove ramekins from baking dish and transfer to a wire rack to cool completely. Once the custards are cool, chill each ramekin, uncovered, for at least 3 hours before serving.