Wash salmon fillets and pat dry. In a small dish mix together the cumin through black pepper. Rub over salmon fillets and allow to rest at room temperature for 30 minutes.
Rinse the rice well under cold running water. In a large pot, bring 12 cups of water to a boil, add in rice, stir once and boil uncovered for 30 minutes. Place a stainer in the sink and pour rice into a stainer. Allow to drain for 10 seconds. Return to the pot, turn off heat source, cover and let rice steam for 10 minutes.
In a small dry skillet, lightly toast the walnuts. Set aside.
While rice is steaming, warm the olive oil and butter in a large skillet over medium high heat. Add in onion, celery and carrot. Cook until onion is wilted. Cover and reduce heat to low. Allow to cook for 4 to 5 minutes or until carrot is barely tender. Add in garlic and zucchini. Cook until zucchini is crisp tender stirring frequently.
When rice is done add to vegetable mixture. Thoroughly combine vegetables with steamed rice. Stir in peas. Cover and allow to rest for a few minutes.
Zest orange then remove peel. Cut and section the orange. Cut sections into thirds if large or into half for smaller sections. Add orange zest and sections to rice mixture along with toasted walnuts. Keep warm while grilling the salmon.
Grill salmon over medium heat until it flakes; approximately 5 to 8 minutes per side. Spoon the rice pilaf onto serving plate and top with grilled salmon. Garnish each serving with fresh cilantro if desired.