It happens to novices and experts alike: you follow the recipe, or maybe stray just the tiniest bit. Everything is going as planned — until it’s not. That perfect cake sinks in the center, maybe while it’s still in the oven, maybe as it cools. What happened? Here’s a primer on the most common reasons cakes (and here we’re mostly addressing cakes or quick breads made with chemical leavening like baking powder or baking soda) develop dreaded sinkholes, and the easiest ways to avoid them.

1. Using a Cake Pan That’s the Wrong Size or Shape

Good recipes specify pan size for good reasons: so the cake can support itself and so the interior and exterior cook perfectly in the same amount of time. The difference between 8- and 9-inch pans may seem insignificant, but it’s about a 25% difference in volume. If a cake pan is too small, the batter may be too deep. It will rise and maybe dome, but if the center is still wet, it will collapse before the structure sets in the center. (It may also spill over the sides of the pan and onto the oven floor, or both!) You can, of course, hold back some of the batter if your pans are too small — a good rule of thumb is to fill a cake pan about two thirds of the way full. You can also adjust oven temperature and baking times to accommodate pan size but that’s a) math, and b) for another article, like this one from pastry chef Hedy Goldsmith.

The shape of the pan matters, too. Many Bundt cakes and moist, sweet coffee cakes baked in tube pans have high ratios of sugar or liquid that can weaken the structure of the cake. It’s the center tube that allows them to rise and set, and the same batter baked in a round or square cake pan may collapse.

2. Baking in an Oven That’s Too Hot or Cold

An oven that runs either too cold or too hot increases the risk of a sunken middle.

To help understand what happens when your oven is too cold, here’s an oversimplified, one-sentence baking primer: creaming butter and sugar creates thousands of little air bubbles that expand when the gasses created by chemical leavening (baking powder and/or soda) hit the heat of the oven. If your oven is too cold, those air bubbles expand slloooowwwwlly, get too big, collide, and form large cells before the structure sets. The big loose structure won’t be able to support the weight of the batter and will collapse. And when the cake sets, it will have a coarse crumb due to those large holes.

If your oven is too hot-well, we’re having a little debate here. Conventional wisdom is that excessive heat causes a peaked, cracked “volcano” center as the leavening explodes quicky and the cake sets in a peak (like muffins, which are usually baked at a higher temperature to create a peak). And that’s a thing. But cake that peaks early (like a high school athlete) can then collapse on itself (like a high-school athlete) if batter is still too wet — essentially the same result that you get from a too-cool oven.

Use an oven thermometer to assure accuracy. Periodically take your oven’s temperature so you know that it is attaining and holding the correct temperature. (In our kitchens, we also use a thermometer every time we turn on the oven.) Ovens cycle about 25 degrees F in either direction to maintain a steady temperature, so place the thermometer in the center of the oven, heat to 350, and take four readings 20 minutes apart. Then divide by 4 — if you are close to 350, the oven is heating as it should. If not, you can either try again, with the oven set higher or lower as warranted, check the owners’ manual to see if you can adjust something yourself or get it recalibrated. Additionally, calibrating with two thermometers in different places lets you locate the oven’s hot and cool spots.

3. Using Too Much Baking Powder or Baking Soda

One of the most common causes of sinkholes is excess leavening. That may seem counter-intuitive since leavening equals lift. But remember our tiny baking lesson? Say you creamed your butter and sugar properly to create lots of air bubbles. If there is too much leavening, the bubbles keep expanding until they bump into each other, hit the top of your cake, pop and … phhhttttt … out goes the gas, down goes the cake. In general: Use 1 to 1 1/4 teaspoon baking powder or 1/4 teaspoon baking soda per cup of flour. In general is the key: If you’ve made a cake that strays from that base and it works, it’s because someone calibrated the amount of leavening needed in sync with liquid, fat, sugar, mixing method, pan size and shape and baking time. The more you bake, the more you’ll understand the relationship of all the variables.

4. Undermixing the Cake Batter

Most recipes warn about the dangers of overmixing and developing glutens, which make a cake tough once flour is added to the wet ingredients. But if you go to the other extreme and undermix, you may not develop enough gluten to give the cake structure, and it won’t be able to support itself as it bakes. Good recipes include visual cues and other tips — how long to mix and the proper look and texture of the batter once it’s properly mixed — to protect you from overmixing and undermixing.

5. Over-Aerating the Batter

Over-aerating — that is, incorporating too much air into the batter — can also weaken the cake’s structure. Remember our primer? For the most part, the air bubbles created by creaming and expanded by leavening are all you need. If you beat in more air when you add eggs and dry ingredients, you can create large bubbles that weaken the cake’s structure and cause it to collapse. We like to beat the eggs separately and then dribble them into the batter while beating; again, good recipes will give you cues and times to help prevent incorporating too much air.

6. Underbaking Your Cakes

Underbaking is one of the most frequent reasons that cakes and quick breads collapse. Baking times are essential guides, but ovens and cake pans vary, so checking for doneness with a cake tester is the ultimate insurance against underbaking. Good recipes tell you what signifies “doneness,” e.g., a clean skewer or one with moist crumbs attached. Our kitchen team has plenty of opinions on what constitutes a proper cake tester. Some prefer a paring knife, to catch a wider portion of cake without creating a hole in the top. Some insist a wooden skewer is best, hole be damned, because the texture of wood grabs underdone batter that can slide off metal, particularly in a very buttery batter. Others opt for skinny metal cake testers. Use whichever tester works best for you, but be sure to push it all the way down to the bottom of the cake pan where there might be wet batter (especially if you are baking a very deep cake, like a Bundt or loaf).

7. Rotating the Cake Pans at the Wrong Time

Most ovens heat unevenly, with hot and cold spots. To compensate, many recipes call for rotating pans halfway through the suggested baking time. But if the center of the cake is still liquid, it may sink when you move the pans. Try to wait until you are about 3/4 of the way through the suggested baking time to open the door and move pans around. And to state the obvious: Keep the light in your oven working and the window in the door clean so you can see how liquid or set your cake is without opening the door. Finally, don’t slam the oven door shut — even if a cake is sturdy enough to manage a move, it may still collapse.

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