When the pasta is done, reserve about 1 cup of the liquid. Drain the pasta and set aside.
Peel and devein the raw shrimp.
Zest and juice the lemon.
Chop the fresh parsley.
Chop the fresh garlic.
Heat a large pan over medium heat to medium-high heat.
Add the olive oil and butter.
Once the butter has melted, add the red pepper flakes and fennel. Cook and stir for about 30 seconds.
Add the shrimp and garlic. Spread the shrimp so that it is a single layer covering the bottom of the pan.
When the shrimp starts to turn pink stir it and spread it out in a single layer again.
After a minute or so add the salt, pepper, lemon zest, and the lemon juice. Stir and cook until the shrimp is done. The shrimp will take anywhere from 3 - 6 minutes to cook completely depending on the size of shrimp. (I usually pull one out of the pan and cut it in half. The grayish raw look should be gone and it will be opaque inside with pink on the outside when it is done.)
Next, add the cooked pasta along with the fresh parsley. Stir well. If you need more liquid, use some of the reserved pasta water.
It is done! Time to eat!
*Adjust cooking time based on the size of shrimp you use.