Adjust an oven rack to the lower-middle section of the oven. Preheat the oven to 300 degrees.
Combine 2 cups of the cream, sugar, and salt in a medium saucepan.
Remove the seeds from the vanilla bean and add them to the pan, submerge the vanilla pod in the cream.
Add the lemon zest.
Bring the mixture to slight boil over medium heat then reduce heat to simmer and let steep 15 minutes to infuse the flavors.
Meanwhile, place a silpat mat (or thin kitchen towel), in the bottom of a large rimmed baking sheet or roasting pan to prevent the dishes from sliding around.
Arrange 8 (4-5 oz) ramekins on the silpat mat.
Add a few blueberries and raspberries to each ramekin.
Bring a large saucepan of water to boil over high heat.
After the vanilla bean has steeped, stir in the remaining 2 cups of cream to cool the mixture along with a tablespoon of fresh lemon juice, more if a stronger lemon flavor is desired.
Whisk the yolks well in a separate large bowl.
Add about 1 cup of the cream mixture into the yolks; whisk until combined; repeat with remaining cream and whisk until evenly colored and thoroughly combined.
Strain through the fine-mesh strainer into a pitcher or bowl; discard the solids in the strainer.
Pour or ladle mixture into the ramekins, dividing it equally among them.
Carefully place the rimmed baking sheet with the ramekins on the oven rack; pour boiling water into the baking pan, being careful not to splash water into the ramekins, until the water reaches two thirds of the way up the sides of the ramekins.
Bake until the centers of the custards are just barely set and are no longer sloshy.
A digital thermometer inserted in the centers should read 170-175 degrees, 30-35 minutes. Begin checking the temperature about 5 minutes before the recommended time.
Transfer the ramekins to a wire rack; cool to room temperature, about 2 hours.
Set the ramekins on a rimmed baking sheet, cover tightly with plastic wrap, and place into the refrigerator for at least 3-4 hours.
Uncover the ramekins, if condensation has collected on the custard surface, place paper towel on the surface to soak up the mixture.
Sprinkle the top of each ramekin with about a teaspoon of turbinado sugar; tilt and tap each ramekin for even coverage.
Ignite the torch and caramelize the sugar carefully.
Refrigerate uncovered, to re-chill, 20-30 minutes (but no longer), serve. Enjoy!