Everything including the egg, butter, and milk must be prepared at room temperature when preparing a typical cake batter. Not too cold and not too warm. Otherwise, it's difficult to emulsify or mix them properly. This can terribly affect the cake structure and make it sink.
Simply toss the fruit in a small bowl with a small scoop of flour and add the lightly covered fruit to your cake mix and follow the rest of the recipe as normal. The light flour coating helps the fruit to 'stick' to the cake mixture better, stopping them from sinking.
Improper blending of the flour and baking powder/soda which can cause holes in the finished cake. Overmixed flour when added to the cake, causing too much gluten. Too much gluten causes a cracked and domed top.
How to fix it: Vigorously beat in a teaspoonful of alcohol-based vanilla extract, or a couple of teaspoons of milk until everything smooths out. Both help to emulsify the fat back into the batter.
Why Does It Matter? When you overmix cake batter, the gluten in the flour can form elastic gluten strands – resulting in a more dense, chewy texture. The white batter looks airier, while the red looks thick and dense.
If it's just little lumps butter, it will be ok to bake. Can you use a slotted spoon to fish out the lumps and then add a small amount of the remaining mix. Whisk until smooth then whisk in the rest of the mixture.
When your butter-sugar mixture looks pale yellow in color and fluffy, stop mixing. If mixed past this point, the butter begins to melt. It will look oily and liquidy, with a grainy texture, or may look white like whipped cream. This means it's been overmixed and cannot be used in your recipe.
It is possible to overmix the butter and sugar. If you overmix, however, the butter will separate out of the mixture and it will be grainy and soupy, so be sure to stop once your butter becomes light and fluffy.
Developing the flour's gluten too much means the cake will rise beautifully in the oven – then sink (a little, or a lot) as soon as you pull it out. And the sinking cake is what makes dense, moist, gluey streaks. Lesson learned: beat butter and sugar and eggs at medium speed.
The most common reason why cakes sink in the middle is that they're underbaked. If a cake isn't fully baked through, the center doesn't have a chance to set and it will sink. This creates a doughy, dense texture in the center of your cake layer.
That's not a cake you'll want to serve. Here's a solution: If you find you underbaked your cake soon after removing it from the oven and it's still hot, pop it back in and bake it at least another 10 to 15 minutes more. Remember to do the doneness test before removing from the oven and cooling.
Room Temperature Butter / Don't Over-Cream
Butter is capable of holding air and the creaming process is when butter traps that air. While baking, that trapped air expands and produces a fluffy cake. No properly creamed butter = no air = no fluffiness. Aka a dense cake.
Cakes typically bake between 325 to 450 degrees F (see chart with Tip #9). Most convection ovens require lowering the temperature by 25 to 50 degrees F, as well as turning off the fan.
Why care about when to stop churning? If churning ceases too soon, much fat is lost to the buttermilk. If over-churned, the butter will contain too much buttermilk and be very difficult to wash clean.
Your butter needs to be “room temperature”, or around 65ºF. If it is too cold, it won't blend with the sugar evenly and will be almost impossible to beat it into a smooth consistency; if it is too hot, the butter won't be able to hold the air pockets that you are trying to beat into it.
Cream the butter and sugar until it turns pale yellow in color and has a light and fluffy texture, which, if using a mixer, takes about one to three minutes on medium speed.
If you don't cream for long enough, your mixture will appear gritty, yellow, and flat.
With a 450-watt stand mixer set to medium speed in a 70°F kitchen, it takes about five minutes for eight ounces of 60°F butter (plus sugar) to hit the proper "light and fluffy" stage. Overworking the butter will eventually beat the air out, making your dough both dense and warm.
Beating softened butter and sugar together, which is called creaming, traps air in the mix, giving the cake more lift and a more open structure. Mixing melted butter and sugar does not trap air, so your cake will be more dense and less open.
Anywhere between 2 and 6 minutes should suffice. The time necessary for mixing will vary with recipe but this should help give you with a ball park idea of mixing time. I hope this information helps as you go forward experimenting with mix times in all of your batter-blending adventures. Happy baking!
Hard butter is more difficult to incorporate into the batter or dough when baking. You might get little chunks of butter that will bake unevenly in cakes and cookies. It is important that softened butter is still cool, and not too warm so it doesn't melt into the batter, but mixes.