Coconut Cookies have bitter underlying taste so I made these coconut cookies for the first time and everything tastes fine except for this added unflattering bitter aftertaste. The taste wasn't pungent but it did make the cookies not enjoyable to eat. The cookies also came out very flat even though it contained baking soda and I chilled the dough. I don't have proper dry measuring cups, so I didn't use any for the cookies. I also used an actual spoon to measure a teaspoon, would this make an actual difference in anything? I also think I might've used a little too much vanilla. What do you guys think could be the problem? 
Recipe: https://www.allrecipes.com/recipe/9589/chewy-coconut-cookies/

Ingredients


1 1/4 cups all-purpose flour 
1/2 teaspoon baking soda 
1/4 teaspoon salt 
1/2 cup butter 
1/2 cup packed brown sugar 
1/2 cup white sugar 
1 egg 
1/2 teaspoon vanilla extract 
1 1/3 cups flaked coconut
Baking requires accurate measurements. In fact most people who bake seriously avoid volume measurements for anything but liquids, and use weight instead (with the exception of small quantities up to about a tablespoon, which affordable scales have only been able to measure accurately in recent years. 

That said, there aren't any particularly bitter ingredients, except the baking soda, and you say the rise wasn't good. However baking soda needs to react with acid, and a shortage of acid would lead to both a poor rise and a bitter flavour. Coconut and butter are both slightly acidic, and even poor mixing  of the soda and acid can cause bitterness and a poor rise