What are the causes of cracking on the top of a fruit cake?

Chris I would like to know this too. I just removed a white Christmas from the oven and it was cracked. It wasn't the last time I looked. I suspect it may be caused by overbaking, or the batter was too dry. Will watch this thread with interest. Ken'

Over baking, too many eggs, heat too high, too much high gluten flour (spring tops vs. soft), leavening system not balanced - too much acid and/or slow reacting acid.

Could be any one or combination of the above. Most common is over baking or temperature too high. Try to eliminate one at a time to trouble shoot. Use a good oven thermometer in the oven to check temp - don't rely on the thermostat of the oven alone. Sudden drafts can cause home ovens to drop temp rapidly and then over compensate heat to recover - especially electric. In convection remember to drop temp 25 -50°F lower than temp in regular oven, and shorten the baking time up to 10%.

Good luck