I've been baking a long time and have never have this happen. I really need advice.
I use the same recipe I've been using for years.
The ingredients are fresh.
The oven is on temperature.
I have tried different recipes i.e. oil and butter cakes.
I'm using XL eggs, 61-66g
I've used different OVENS.
All the cakes are mixed EXACTLY according to the recipe.
I've put two pans in at once.
I've put one pan in at a time.
I just don't know any more.
I really am ready to throw in the towel.
The center of a cake caving in is a sign that the cake is not done. If it were me, I would purchase a thermometer to check your oven temp. Maybe there is something wrong with your oven that it is not heating up to the temp that you are setting. Just a thought.
If you're sure your oven temp is fine, perhaps a thermometer that you stick in the cake to read the temperature will tell you if the cake is done before you take it out of the oven will give you more information about why it's caving in.
It may be because of the structure problem.
You may be using wrong type of flour. Did you use bleached flour or unbleached flour?If using unbleached flour for a butter cake, the cake will dip in the center about 5 minutes after baking. This is because the smooth flour particles of unbleached flour cannot effectively hold the butter is suspension.
Too Weak a Structure
This is usually due to too much leavening. Try dropping the baking powder by 1/4 teaspoon.
The larger the cake, the less amount of baking powder per cup of flour is used. This is because the distance from the sides of the pan to the center are greater so that they batter needs a stronger structure to support itself.
Excellent points being made here! Also, if this is a larger cake, perhaps baking at t lower temp but for a longer period of time might help. That way your center is not mush by the time your sides are firm and crispy. Good luck, and please let us know if you figure it out!