Greek Shrimp and Orzo Salad

Ingredients

• 1 pound dried orzo
• 2 1/2 pounds fresh shrimp, peeled and deveined (but with the tails on)
• 1 1/4 cup scallions, chopped (both the white and green parts)
• 1 1/4 cup finely chopped flat-leaf parsley
• 1 1/4 cup chopped fresh dill
• 2 English cucumbers, left unpeeled but seeded and diced
• 1 red onion, diced
• 1 pound feta cheese, crumbled into large chunks
• 3/4 cup freshly squeezed lemon juice
• 1 teaspoon lemon zest
• 1/3 cup olive oil, plus more for roasting the shrimp
• 1 Tablespoon Dijon mustard
• 2 1/2 teaspoons sea salt
• 2 teaspoons freshly ground black pepper
• 2 lemons, thinly sliced into rings