Preheat your oven to 400°F (200°C) and line a small baking sheet with parchment paper.
Slice the zucchini and yellow squash into half-moons and place them on the baking sheet.
Toss the vegetables with half of the sea salt, black pepper, and garlic powder, then roast for 15 minutes until tender.
While the vegetables roast, bring 3 tablespoons of water to a boil in a small saucepan.
Stir in the dry couscous, cover with a lid, remove from heat, and let it sit for 5 minutes.
Season the salmon fillet evenly with the remaining sea salt, black pepper, and garlic powder.
Heat the olive oil in a non-stick skillet over medium-high heat.
Place the salmon in the skillet and sear for 4 to 5 minutes until a golden crust forms, then flip and cook for an additional 3 minutes.
Fluff the couscous with a fork and stir in the fresh parsley and lemon juice.
Plate the salmon over the bed of fluffy couscous and serve with the roasted squash medley.