Upvote:5
Maybe, maybe not. It is unfortunately difficult to tell in advance.
mdewey already linked to the relevant page from the Australian Department of Agriculture. They only give you guidance on which products you have to declare. If in doubt, you should declare any kind of food, plant or animal matter when entering Australia. They have very strict rules on what is allowed to import and the penalties can be quite severe if you fail to declare something.
I don't know the exact content of your fruit cake, but it will likely contain some of the following products, which have to be declared:
After you have declared the food on arrival, it will be inspected by a biosecurity officer, who on a case-by-case basis will decide if you are allowed to take it in or not.
Upvote:7
The Australian Border Force has a new web site on what you can bring to Australia. Under "Top items" you'll find this: