Why did my cake dome and crack on top?

Why the middle rises last and hardest, the two changes that flatten it, and how to level a cake that has already domed.

Difficulty: beginner
Time: 15 min
Read: 3 min

Short answer

The edges set before the middle, so the middle carries on rising and splits the crust. Lower the oven by about 10-20°C and use a damp cake strip around the tin — that slows the edges so the whole thing rises evenly.

A domed, cracked cake is a sign the oven was slightly too hot rather than that anything was wrong with the mixture. It tastes perfectly good; the problem is only that it will not stack or ice neatly.

Step by step

Understand the mechanism.The outside of the tin heats first, so the batter at the edges sets while the middle is still liquid. The middle keeps expanding, has nowhere to go but up, and breaks through the crust that has already formed on top.
Lower the oven temperature.10-20°C down and a slightly longer bake. A gentler heat lets the middle rise at the same rate as the edges rather than racing to catch up.
Use a cake strip around the tin.A damp fabric strip, or a folded strip of wet tea towel secured with a pin, wrapped round the outside. It keeps the edges cooler so the whole cake rises together. This is the single most effective fix.
Check the oven's real temperature.If it runs 20°C hot, every other adjustment is compensating for the wrong thing. An oven thermometer settles it.
Do not overfill the tin.About two-thirds full. An overfilled tin has to rise a long way and does most of it in the middle, which exaggerates the dome.
Check you are not over-raising.Too much baking powder or bicarbonate produces a violent early rise that outpaces the setting. Measure it properly, and check the recipe if you have scaled it.
Do not over-mix after the flour.Developed gluten makes a stronger batter that traps gas harder and pushes upwards rather than spreading. Fold until just combined.
Reconsider the tin material.Thin dark tins heat the edges fast and make doming worse. A heavier, lighter-coloured tin gives a flatter result.
Level it after baking if it has domed anyway.A long serrated knife across the top while the cake is completely cold, or a cake leveller. Save the trimmings — they make a good base for a trifle or cake truffles.
Consider inverting it.For a layer cake, turn the cake upside down so the flat base becomes the top. That removes the problem entirely without cutting anything.
Accept the crack on some cakes.Loaf cakes, madeira and banana bread are supposed to split along the top. On those, the crack is the intended appearance rather than a fault.

Tips

Cake strips are inexpensive and reusable, and a wet folded tea towel does the same job for nothing.
Level cakes only when completely cold. Warm cake tears and compresses under the knife.
If the dome is slight and the cake is being iced anyway, ignore it. Not every imperfection needs correcting.

Common mistakes

Filling the tin too full — The mixture has further to rise and does most of it in the centre, which exaggerates the dome and the crack.
Levelling a warm cake — It tears and compresses rather than cutting cleanly. Wait until it is completely cold.

If it doesn't work

High dome with a deep crack

Cause: Oven too hot — edges setting well before the centre — Fix: Reduce by 10-20°C, use a damp cake strip around the tin, and bake slightly longer.

Domed but no crack

Cause: Mild version of the same thing, or an overfilled tin — Fix: A cake strip usually resolves it. Otherwise level it or invert the cake.

Domed and the texture is coarse

Cause: Too much raising agent — Fix: Measure it accurately, and check the quantity if you have scaled the recipe from its original size.

Questions people ask

How do I stop a cake doming in the middle?

Lower the oven by 10-20°C and wrap a damp cake strip around the outside of the tin. That keeps the edges cooler so the whole cake rises at the same rate rather than the middle catching up last.

Is a cracked cake ruined?

Not at all — it is a cosmetic issue and the cake tastes the same. Level the top with a serrated knife once cold, or turn it upside down and use the flat base as the top.