01. Preheat oven to 350°F.
02. Grease and flour 24 cm IronPot cast iron pan.
03. In a large bowl, beat butter and sugar until light and fluffy.
04. Add the eggs, one at a time, beating well after each addition.
05. Stir in the vanilla extract.
06. In another bowl, whisk together the flour, baking powder and salt.
07. Gradually add the flour mixture to the butter mixture, alternating with the milk and beating until well blended.
08. Stir in the lemon zest and cranberries.
09. Pour the batter into the prepared pan and smooth the top.
10. Bake for 30-40 minutes until a toothpick inserted in the center comes out clean.
11. Leave to cool in the tin for 10 minutes before removing to a wire rack to cool completely.