I have always been confused about cooking with lemons. I use zest & juice often - however, it has been my experience that adding sliced lemons at the last few minutes of a Picata sauce brought out the bitterness from the lemon's white pithy part. Yet I have come across several recipes that use the whole lemon - even putting a whole lemon in the food processer to make a puree. Please explain what I might be doing wrong.