Sprinkle the raspberries and blueberries into eight, flat 4-ounce ovenproof dishes (the dishes won’t be going in the oven, but they must be able to resist the heat of the torch for brûléeing).
Heat the cream on medium low with the scraped seeds of the vanilla bean pod (and the pod, too, if you wish) and the lemon zest. If using vanilla bean paste, whisk it into the cream and heat. Heat the cream for about 5 minutes, watching so that it doesn’t boil over.
Bring a second pot filled with an inch of water to a gentle simmer. In a metal bowl, whisk the egg yolks, sugar and lemon juice together. Place the bowl on top of the pot of simmering water and whisk the egg mixture until it has doubled in volume and is a pale buttery colour, about 3-4 minutes. Remove the bowl from the pot of water.
While whisking, slowly pour the heated cream into the whipped egg mixture and return the entire mixture to the pot, stirring with a wooden spoon or silicone spatula over medium heat until the custard thickly coats the back of a spoon, about 4 minutes. Pour the custard through a strainer and then pour it slowly over the berries, stirring the berries slightly just to ensure they are fully coated and covered. Cool the custards for 15 minutes, then chill, uncovered, until set, at least 4 hours.
To serve, sprinkle each custard with a thin layer of sugar. Carefully ignite a kitchen butane torch and caramelize the sugar by moving the torch back and forth over the custard, about an inch or 2 away from it. Sprinkle another thin layer of sugar over the first layer and torch it, repeating another 2 times or until the desired caramel layer is achieved. Serve immediately.