Add shrimp, lemon zest, and pepper to a bowl. Toss well to coat.
Heat oil in a medium skillet. Add shrimp. Cook, stirring frequently, about 5 minutes, or until shrimp are cooked through and opaque. Remove shrimp, set aside, and keep warm.
Add butter to skillet. Add onions, garlic, and salt. Stir well. Cook, stirring frequently, until onions are translucent, about 2 minutes. Stir in orzo and cook an additional 2-3 minutes, or until orzo is toasty, stirring frequently to prevent burning.
Add broth and peas and bring to a simmer. Simmer 7-8 minutes or until orzo is done and liquid is absorbed.
Add shrimp to skillet along with 1/4 cup cheese and lemon juice. Stir well.
Transfer to a serving bowl and top with remaining cheese and chopped parsley. Garnish with lemon, if desired.