Season the tops of the salmon with 1 teaspoon salt and ¼ teaspoon pepper.
Heat the oil in a large, deep skillet (or braiser) over medium-high heat. When hot, add the salmon filets, seasoned side down, and sear until a golden-brown crust has formed, about 3 minutes. Transfer to a clean plate and set aside. The salmon will finish cooking with the couscous; you just want a golden color on the top.
Reduce the heat to medium. Add the onion and garlic and cook, stirring, until tender, about 3 minutes.
Add the couscous and cook, stirring, toasting the couscous but being careful not to burn, 2 to 3 more minutes.
Add the herbs (rosemary, thyme, and parsley) and white wine. Stir and cook until the wine is absorbed in the couscous, about 1 minute.
Add the broth, lemon zest, onion powder, garlic powder, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Stir to combine. Bring to a rapid simmer, then immediately reduce the heat to medium-low. Cover and cook until most of the liquid is absorbed, about 8 minutes.
Remove the lid and stir in the butter and Parmesan until well combined and the butter is melted. Nestle the salmon filets, browned side up, into the couscous. Cover and continue to cook until the salmon is cooked through, 3 to 5 more minutes, depending on the thickness of your salmon.
Remove from the heat. Garnish with more fresh thyme and serve with lemon wedges. Enjoy!