1. In a small bowl, dissolve yeast in the 70ml of warm water and set aside. Place the butter, sugar, and salt in a large bowl mixer. Add the boiled milk, and using the paddle attachment or whisk, mix until all the butter has melted and the milk is just warm. Add the vanilla, eggs, and yeast, and mix until well combined.
2. Add the flour and lemon zest, and sultanas or raisins, and mix thoroughly. The dough will be of a thick cake batter consistency.
3. Heat the oven to 180ËšC, 350ËšF or gas mark 4. Lightly coat a 10-inch Bundt pan or tube pan with cooking spray. Pour the batter into prepared pan and cover lightly with a damp cloth or clingfilm. 
4. Leave to rise in a warm place until it doubles in size or until the dough reaches the top of the pan.
5. Bake for about 40 to 45 minutes or until a toothpick inserted near the centre comes out clean.
6. Cool on a wire rack.
7. Make the icing made by whisking together confectioners' sugar and lemon juice, and add water to make a paste. Drizzle over the cake to serve.