Preheat Oven 350f, 180c, gas mark 4.
Sieve the flour, salt, baking powder.
Then add the eggs, milk, butter and vanilla essences whisk till combined.
Grease and flour a 9 x 13 inch baking dish and transfer the batter in it.
Now mix butter, brown sugar, plain flour, cinnamon powder and drop over the cake mixture evenly, swirl the topping and cake mixture with a knife.
Bake for 28 to 32 minutes or till checked with a toothpick comes out clean.
Mix powder sugar, milk, vanilla.
Once the cake is baked spread the frosting on the cake.
Serve with tea or coffee.