Add the olive oil to a large skillet or medium pot over medium heat. Add the onion and salt, and stir to coat. Cook for 4 minutes.
Add the broth, cover, and bring to a simmer.
Add the orzo and cook for 12-14 minutes, stirring occasionally, or until the liquid is almost absorbed and the pasta is tender. (It's okay if there is some liquid left when the pasta is tender as it will continue to be absorbed by the pasta.)
Stir in the Parmesan, cream, butter, and peas; add lemon juice and zest, if using. Let sit for about 5 minutes to thicken, if needed. Serve warm.
Notes
Store leftovers in an airtight container for up to five days. To reheat, sprinkle with water and cover with a damp paper towel or wax paper. Warm in 30-second increments, stirring in between, until heated through.
Season to taste with salt and pepper as you like.
Adults may enjoy this topped with crushed red pepper.
Substitute vegetable broth for the chicken broth to make this vegetarian.
Use gluten-free orzo if needed and additional broth in place of the cream to make this dairy-free. Many people like nutritional yeast as a nondairy alternative to Parmesan cheese.