Preheat oven to 375 degrees F. Butter a flat-bottomed 2-quart souffle or baking dish. Set a kettle of water on to boil. Crush the raspberries, add 2 tablespoons of the sugar, and let sit for a few minutes to get juicy.
Cream the butter, gradually adding the remaining sugar. Mix in the flour, salt, and lemon juice. Place the egg whites into a clean mixing bowl. Add the yolks one at a time to the butter mixture; then add the milk. Beat the egg whites until stiff, and fold into the batter.
Pour the raspberries and juice into the prepared dish. Spoon the batter over the top. Set the dish into a deep roasting pan and pour boiling water into the pan to come one-third of the way up the side of the dish. Bake for 45 to 50 minutes, or until the top is firm. The cake separates into two layers while baking – a moist, lemony sponge on top and a raspberry pudding below to spoon over the cake.