Preheat your grill to medium-high and brush the salmon fillets with olive oil, then season with salt, pepper, and garlic powder.
In a large pan over medium heat, warm olive oil and sauté the garlic until fragrant (about 1 minute), then stir in the orzo and toast for 2 minutes.
Add the cherry tomatoes, crushed tomatoes, chicken broth, water, oregano, salt, and pepper, then bring to a simmer.
Cook the orzo uncovered for 10–12 minutes, stirring occasionally, until the liquid is mostly absorbed and the orzo is tender.
While the orzo cooks, grill the salmon skin-side down for 4–5 minutes, then flip and cook another 3–4 minutes, or until just cooked through.
Remove the salmon from the grill and let it rest a minute or two.
Stir parmesan (if using) into the orzo and spoon it onto plates, then top with grilled salmon and garnish with lemon wedges and herbs.