I have made 2 batches of this recipe and BOTH times it has sunk in the middle while finishing baking in the oven! I need a good one by tomorrow! Am I over-beating or is it because I've switched to the creaming method instead of the way it says to incorporate? It has almost 6 tsp of powder and was wondering if this could be the problem? Thanks in advance for your help!

Recipe used is:

Vanilla Buttermilk Cake
Sky High: Irresistible Triple-Layer Cakes

Makes one three-layer 9-inch round cake [Equivalent in batter to an 8-inch square; we scaled it up for a 10-inch square/middle tier of the wedding cake]
3 3/4 cups cake flour
2 1/2 cups sugar
1 tablespoon plus 2 3/4 teaspoons baking powder
1/2 teaspoon salt
2 1/2 sticks (10 ounces) unsalted butter, at room temperature
1 1/4 cups plus 1/3 cup buttermilk
5 whole eggs
2 egg yolks
2 1/2 teaspoons vanilla extract
1. Preheat the oven to 325°F. Butter three 9-inch round cake pans. Line the bottom of each pan with a round of parchment or waxed paper and butter the paper.
2. Combine the cake flour, sugar, baking powder, and salt in a large mixer bowl. With the mixer on low speed, blend for 30 seconds. Add the butter and 1 1/4 cup of the buttermilk. Mix on low speed briefly to blend; then raise the speed to medium and beat until light and fluffy, 2 to 3 minutes.
3. In a smaller bowl, whisk together the whole eggs, egg yolks, vanilla, and the remaining 1/3 cup buttermilk until well blended. Pour one-third of the egg mixture into the cake batter at a time, folding it in completely after each addition. There will be 9 cups of batter; our 3 cups batter into each pan.
4. Bake for 26 to 28 minutes, or until a cake tester or wooden toothpick inserted in the center comes out clean.
5. Turn the layers out onto wire racks by placing a rack on top of a pan, inverting it, and lifting off the pan. Peel off the paper liners and let cool completely. When the layers have cooled, place a cardboard cake board on top of a layer, invert again, and lift off the rack. To make the layers easier to handle, wrap them on their boards completely in plastic, so they dont dry out, and refrigerate them.

I adapted a Magnolia Bakery recipe and it turns out perfect every time. Makes 6c batter:

3c cake flour (self-rising)
2c sugar
1 stick butter + 1 tbsp oil
4 large eggs
2 tsp vanilla extract
1c buttermilk
2 tsp baking powder
1/2 tsp salt

Use the creaming method for this recipe. Bake at 350 for cakes 8in or smaller, 325 for 9in or larger and use a flower nail in the larger tins.

Thank you so much for your response. Unfortunately I had begun to bake my third batch before I was notified of your post. On the good side my third batch came out perfect!! I followed the mixing instructions for the recipe (who knew that would work?) and it baked up just fine!

I had read somewhere on here that the creaming method could be interchanged with recipes sometimes...I guess this was NOT one of them.

Thanks again and I will definitely give your recipe a try!

nati, this is the only, only vanilla recipe I make.

It comes out perfect all the time.

You might be overbeating it. I make it exactly as it is, it only takes about 3 to 4 minutes to mix.

The recipe I have calls for 4 1/2 tsp baking powder.

The post is 18 months old ...
Note
One 8" triple layer cake recipe - 4 1/2 teaspoons baking powder
One three-layer 9-inch cake - 1 tablespoon plus 2 3/4 teaspoons baking powder [5 3/4 teaspoons]