Heat the olive oil in a large skillet over medium heat.
Add the diced onion and sauté until translucent, about 3 minutes.
Add the minced garlic and cook 30 seconds until fragrant.
Add the whole wheat orzo to the skillet and stir to coat in the oil; sauté about 1 minute.
Stir in the diced tomatoes, Italian seasoning, and chicken broth, then bring to a boil.
Reduce heat to a simmer and cook, uncovered, about 8 minutes, stirring occasionally, until the orzo is nearly al dente.
Stir in the Parmesan cheese until combined.
Season the salmon with salt and pepper, then nestle the pieces into the orzo mixture.
Cover the skillet and simmer 8–10 minutes, or until the salmon is cooked through and the pasta is tender.
If there is excess broth, remove the lid and simmer briefly to reduce to your desired consistency.
Garnish with chopped parsley and serve.