Preheat oven to 350° F and lightly grease an 8"x8" baking dish.
In a large mixing bowl combine the milk, egg, butter, sugar, salt and the juice of the lemon. Whisk until well combined.
To the wet mix, using a wooden spoon, stir in the flour and baking powder.
Pour the batter into the baking dish and bake for 30-35 minutes, until a toothpick inserted in the center comes out clean.
Set aside to cool.