In a large skillet, heat the olive oil over medium heat. Add the shrimp and cook for 2-3 minutes until they turn pink. Remove the shrimp from the skillet and set aside.

In the same skillet, add the diced onion and sauté for about 3-4 minutes until translucent. Add the minced garlic and cook for an additional 1 minute.

Stir in the orzo pasta, chicken broth, diced tomatoes (with their juice), Italian seasoning, and red pepper flakes if using. Bring the mixture to a boil.

Reduce the heat to low, cover the skillet, and simmer for 10-12 minutes, stirring occasionally, until the orzo is tender and has absorbed most of the liquid.

Once the orzo is cooked, stir in the chopped spinach and cooked shrimp. Cook for another 2-3 minutes until the spinach is wilted and the shrimp are heated through.

Remove from heat and stir in the grated Parmesan cheese. Season with salt and pepper to taste.

Garnish with fresh parsley before serving.