Heat the olive oil in a large pan over medium heat. Add the sliced sausage and cook until browned, then transfer to a plate and set aside.
In the same pan, add the diced onion and red bell pepper. If needed, add a little more oil and cook for 4–5 minutes, until softened.
Stir in the minced garlic and cook for about 30 seconds, just until fragrant.
Add the uncooked orzo and cook for 1–2 minutes, stirring frequently, until lightly toasted.
Pour in the chicken broth and stir in the Cajun seasoning. Bring to a boil, then reduce the heat and simmer uncovered for 8–10 minutes, stirring occasionally, until the orzo is tender and most of the liquid has been absorbed.
Stir in the half-and-half, parmesan cheese, and cooked sausage. Cook for another 1–2 minutes until everything is warmed through and creamy.
Add the spinach and cook until wilted, then stir in the lemon juice.
Garnish with extra parmesan and fresh parsley if desired, then serve.