Preheat oven to 170C.
Sift flour with baking powder and salt and set aside.
Cream butter in a mixer at medium high speed until creamy (about 2 mins). Add sugar gradually and continue beating for 4 mins until light and fluffy.
Reduce the mixing speed of the mixer to low and add eggs one at a time mixing until well mixed.
Add the citrus zest and vanilla extract.
Add flour mixture in 3 additions, alternating it with cream (added in 2 additions).
Pour into 2 lined 3″x 7″ pound cake mold and bake for 60-70 mins or until the cake turns brown and a testing skewer comes out clean. (Trish Boyle had baked this at 162C but I had to use a slightly higher oven temperature to ensure that the cake is cooked through without dense uncooked spots)