What happen at the bottom of the cake?! Very dense and compact.

We need to know the exact recipe you used & bake time & temp to try to help. 

As kakeladi said, it would be helpful to have more information.  If I had to blind guess, I would say the batter was over mixed, but it is possible there was too much liquid or fat in the recipe, as well.  Here is a post from King Arthur regarding this situation.

https://www.kingarthurbaking.com/blog/2014/07/15/how-to-prevent-dense-gluey-streaks-in-your-cake

Like Sandra, I'll bet for a too much liquid, too much fat or a cold/disturbed oven during baking. Have you tried that same recipe before?

Hi all of you!

Yes, this i s a recipe that I use for many years, but in the past, the ratio to the sour cream was 3/4 cup instead 1 cup.

Here the recipe:

• 3 cups all-purpose flour
• 2 cups sugar
• 1 cup of butter
• 4 eggs
• 1 cup of buttermilk (I use 3.25% milk with white vinegar into it)
• 1 cup of sour cream
• 2 1/4 tsp of Baking powder
• 1 tsp of baking soda
• 3/4 tsp of salt
• and the famous vanilla. I put alot. 6 tbsp. :) A great taste of vanilla + vanilla bean.

I change the ratio of the sour cream because I found (in my memories) that the cake stay more moist longer.

The bake time temp is 325F. Also here, change the temp from 350 to 325 because I read an article this article: https://thecakeblog.com/2015/04/baking-temperature-comparison.html

Baking time vary but of course, more long than 350 F :)

This is a recipe that I start with a base and modify my own for a great success. Dont know what you suggest...? MAybe add a little bit flour?

I will wait your news!

Also, If I compare to this recipe that I use for my almond cake (here no liquid but same ratio, but more fat from the sour cream) and the cake is perfect. Probably because the 1 cup more of almond meal?

https://www.canadianliving.com/food/baking-and-desserts/recipe/almond-lemon-wedding-cake

Also, If I compare to this recipe that I use for my almond cake (here no liquid but same ratio, but more fat from the sour cream) and the cake is perfect. Probably because the 1 cup more of almond meal?

https://www.canadianliving.com/food/baking-and-desserts/recipe/almond-lemon-wedding-cake

Well, the basic difference in the two recipes is that the Almond-Lemon cake has 1 cup of butter and 2 cups of sour cream, plus the cup of ground almonds and this one has 1 cup of butter, 1 cup of buttermilk, and 1 cup of sour cream.  If you prefer the full cup of sour cream, I would recommend cutting back 1/4 cup on the buttermilk or as much as a half cup, depending upon how thin the batter.  

Thank for your reply!! 

You are welcome.  Hope it helps.  That is what I would try.