Most common questions used to investigate
Is the moisture level of your cake correct?
Did you follow the recipe correctly, adding each ingredient at the correct time?
Is your oven heated to the correct temperature?
Did you remove your cake from the oven before it was fully baked?
Did you over beat the batter?
Did you open the oven door before the batter set?
Did you close the oven door too sharply?
Common conclusions
Your cake collapsed because your cake is either too moist or not moist enough. Try weighing your ingredients rather than measuring. If you live in a humid area, try keeping your dry ingredients in the freezer.
Your cake collapsed because you might have added ingredients at the wrong time. Try reading the recipe first and laying out all your ingredients ahead of time.
Your cake collapsed because your oven temperature is incorrect. Try checking your oven periodically with a heatproof thermometer to see if your dial is accurate.
Your cake collapsed because it was under cooked. Try checking your cake by poking it with a toothpick or skewer. If fully baked - the
Your cake collapsed because you incorporated too much air into your batter.
Your cake collapsed because you opened your oven door to early. Try to open your oven door to check your cake only once the cake is about 80% done.
Your cake collapsed because you closed your oven door too sharply. Try to close your oven door softly especially in the early baking stages.
Unfortunately, we were unable to determine the reason your cake has collapsed.
References
https://www.mybluprint.com/article/no-more-cake-fails-heres-how-to-keep-your-cake-from-falling-and-save-it-when-it-does
https://delishably.com/desserts/Baking-Tips-Why-a-Cake-Sinks-in-the-Middle-and-How-to-Stop-It
https://lindyscakes.co.uk/2009/05/13/why-do-my-cakes-sink-in-the-middle/
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