baking soda/baking powder switch in recipe

My two cents: your sugar is a bit too much, and that makes the cake on the heavier side. There is a reason why bundt cakes with equal amounts of flour to sugar are baked in special pans. Alternatively if this is not a birthday cake, keep the batter as you like it, and bake in that kind of pan.

Hillarybee's advice is perfect. Don't decrease the baking soda. It is proportional to the amount of acid: 1/2 teaspoon for every 8 ounces of acidic ingredient.

I am not high altitude. The buttermilk is Organic Farms. There is salt in the recipe. I am confused about the baking soda. I thought too much would make the cake sink. I understood 1/4 tsp per 1 cup flour. SInce the recipe has double the amount of baking soda, I thought decreasing it would prevent sinking. I am not sure why increasing the baking soda would help. My thinking was too decrease the baking soda. Can you clarify? Sorry for being so dense!

Would the tsp of vinegar be the first thing to try, leaving the baking soda the same?

Also, what is your altitude? Do you live in Colorado, Washington state or somewhere else with high altitude?

Sounds basic. You might have to give it two separate gos to figure out what the problem is. Regardless, please do add about 1/4 tsp of salt. Other options: 1) Increase the baking soda and leave the buttermilk alone. 2) Increase acid in the buttermilk, via lemon juice or vinegar and leave the baking soda alone. 3) Increase acid, increase baking soda.

Try those out and see how it goes. Are you using cultured buttermilk? or Buttermilk with butterflakes added? Because that will make a difference. Go for cultured if you can.

There is one stick of butter, 3 eggs, AP flour, salt, 1 1/2 cups sugar. Butter is softened and creamed with the sugar, and the eggs are added. Flour and buttermilk are added alternately.

Good information, ChefOno. But if you want to work with say, whole wheat, or maybe a fruit puree, etc. You will need to increase the leavening agent. I don't like to use bleached flour at all, for cakes or any other purpose.

Stephanie, can you tell us about this cake and it's other ingredients? Is this an oil based cake? Butter? AP flour? What kind of buttermilk are you using?

You could also add about a teaspoon of vinegar to the buttermilk instead of adding baking powder. Whenever you are working with an acid, baking powder isn't super effective.

Maybe this will help, from Rose Levy Beranbaum:

Dipping is always a structural problem. It can be either of the following:

The Wrong Type of Flour

If using unbleached flour for a butter cake in which the butter is used in softened form, as opposed to melted as for a genoise, 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. So use bleached cake flour or bleached all-purpose flour.

Too Weak a Structure

This is usually due to too much leavening. Try dropping the baking powder by 1/4 teaspoon.

I'd be more apt to leave the soda as it is and add baking powder plus a pinch of salt. So you might go with 1 tsp Baking Powder, 1/2 tsp Baking soda and 1/4 tsp salt.

I found this episode of Kitchen Confidence VERY helpful in explaining it all!

http://www.food52.com/blog/search?query=chemical+leaveners