Clean and pat dry shrimp, season. Add butter to skillet and sauté until shrimp are cooked. Transfer to a dish on the side, leave butter in pan.
In same skillet, add in onion and garlic. Cook until translucent. Add in orzo pasta, let cook together and toast for a few minutes.
Add in 2 cups of broth, let come to a simmer and let cook until orzo is al dente and most liquid is absorbed. (Stir occasionally to prevent sticking). Add in a little more broth at a time if needed.
Once orzo is al dente, add in more seasoning, asparagus and spinach. Squeeze in 1½ lemons and let cook until spinach is wilted and asparagus is cooked with a slight crunch.
Add shrimp back in. Toss to marry flavors. Squeeze with last lemon half and sprinkle more Parmesan.