Preheat the oven to 400°. Cook pasta in salted water for two minutes less than the package directs. Reserve about a cup of pasta water--I use a coffee mug or measuring cup to carefully dip some out of the pot--then drain pasta and set aside.
Melt the butter in a large skillet over medium heat. Add the zest and juice of one lemon (absolutely no seeds!), plus ½ t. salt and ½ t. pepper. Add ½ the parsley, the cream if using, and 1/2 cup of pasta water. Whisk vigorously for a minute. Turn heat to very low while you make the shrimp.
In a bowl combine the shrimp, the rest of the parsley, oregano, garlic powder, feta, breadcrumbs, and olive oil. Add the zest of another lemon plus the juice of half that lemon. (You can whisk the juice of the other half into the sauce if you like.) Toss the shrimp mixture until well combined. Spread on a sheet pan in a single layer. Slice the last lemon thinly and add to the sheet pan, but not on top of the shrimp and breadcrumbs.
Roast the shrimp for 10 minutes, or until the shrimp is uniformly pink and the crumbs are nicely browned. Remove from the oven.
About 2 minutes before the shrimp is done, turn the heat under the skillet back to medium, and taste the sauce for seasoning. Adjust salt and pepper if needed. If your sauce is too sour, add a little more salt. Add the pasta to the pan and toss with the sauce. If the sauce is too thick, you can add a little more pasta water.
Serve noodles topped with shrimp and breadcrumbs. Use the roasted lemon slices as garnish.