Could you tell me what is the reason for the cake being bitter in taste?
Investigate tasting each ingredient separately and spitting out the flour. Sniff around. Even check the pans. Some things can go rancid and even vanilla can go bad.
it’s a common problem, baking soda. Switch to only baking powder and or use way less baking soda. Also refrigerate after you make the cake this helps with less deterioration of the soda.
Please post your recipe.