1. Preheat the oven to 175°C. Grease four 5-ounce ramekins and sprinkle them with sugar, tapping out any excess. Place these in a larger pan (such as a roasting pan).
2. Sprinkle the berries evenly on the bottom of each dish.
3. Stir the sugar, flour, lemon zest and salt to combine. Add the lemon juice, milk and egg yolks to this and whisk until smooth.
4. Whip the 2 egg whites until they hold a soft peak when the beaters are lifted. Fold this into the batter until fully incorporated and divide this between the ramekins. Pour boiling water around the baking dish and bake for about 35 minutes, until golden brown on top. Allow the cake to cool for 15 minutes in the water bath, then remove the ramekins from the water and continue cooling to room temperature then chill for at least 3 hours.
5. For the bumbleberry sauce, place the berries, sugar and lemon juice in a saucepot over medium heat and bring to a simmer. Continue to simmer, stirring occasionally, until the berries are tender and the liquid has reduced by a third, about 15 minutes. Cool the sauce to room temperature, then chill before serving.
6. For the meringue, whip the egg whites and lemon juice on medium-low speed until foamy the slowly add the sugar, increasing the speed to high and whipping until the whites hold a stiff peak when the beaters are lifted.
7. Run a palette knife around each of the chilled lemon desserts and invert it onto individual plates. Spoon the meringue into a piping bag fitted with a large star tip and pipe on top of each dessert. Use a butane kitchen torch to brown the meringue (alternatively, you can turn the desserts out onto a parchment-lined baking tray, pipe and then bake the meringues for 2 minutes in a 450 F oven) and serve immediately with the bumbleberry sauce.