“As jamaro says, the pith (white part of the peel under the yellow zest) is terribly bitter.

“The zest itself, though, is the difference between pretty good lemonade and the tangy, fragrant lemonade you deserve. The zest is full of delicious citrus oil.

“I slice the zest from the lemons before slicing or squeezing them. I use a sharp knife, since it’s easier to control that a vegetable peeler. Then with the edge of the knife, trim off any residual patches of pith from the zest. Now you have all the rich gorgeous lemon flavor without any of the vile pith.

“If you want to use plain ole sugar & water, you can make a nice lemonade by mashing the sugar and lemon zest together, sure, but it’ll be a bit grainy. So, if you’re making kick-ass lemonade, then why not make kick-ass lemonade by making simple syrup?

“So easy. Put 1 part sugar in a saucepan. On top, dump 1 part water. Don’t stir. Mark a cross in it with your finger or a wooden spoon; this lets the water permeate the sugar a bit. Put over medium-high heat; boil (not a raging boil, and do not stir) about five minutes. This dissolves the sugar crystals into the syrup, and they’ll stir right into the water and juice to make a smooth lemonade.

“Here’s a trick I like: when the simple syrup has cooled a bit, toss in the strips of lemon zest. The heat releases the oils into the syrup, and when you add the lemon juice and water, your lemonade will be like a glass full of summer.

“(Psst: if you make extra simple syrup with lemon, you can keep it in a jar in the fridge. I keep mine in an old honey container with a flip-top, so it’s easy to squeeze out into a glass. Try this: in a tall glass, squirt a bit of lemon syrup, a splash of voka or gin, and fill the rest of the glass with seltzer or club soda. Mmmmmm. Refreshing.)”

[Stolen from this Ask.Me comment]