Heat the oven to 180°C and line a 12 x 5 inch loaf tin with baking paper. Start by sifting together the flour, baking powder and salt and put aside. In a bowl, beat together the sugar, softened butter, lemon zest and vanilla until light and fluffy. Beat in the eggs, one by one till the mixture is light and creamy. Next, stir in the flour mixture in ⅓, alternating with the yogurt. Finally, carefully coat the raspberries in the tablespoon of flour and mix into the cake batter. Spoon into the prepared cake tin, even out and bake for approximately 55-60 minutes. Allow to cool down completely. To decorate, mix the icing sugar with the vanilla and enough lemon juice to make a glaze` icing and spoon over the cake. Decorate the top with fresh raspberries and extra lemon zest.