Adjust rack to top position and preheat oven to 450 degrees. Wash and dry produce.

Trim and thinly slice scallions, separating whites from greens.

Heat a drizzle of olive oil in a small pot over medium-high heat. Add scallion whites and cook until fragrant, 30 seconds. Stir in rice, 1¼ cups water (2¼ cups for 4 servings), and a pinch of salt. Bring to a boil, then cover and reduce heat to low. Cook, covered, until rice is tender, 15-18 minutes. Keep covered off heat until ready to serve.

While rice cooks, finely chop walnuts or crush in their bag with a heavy-bottomed pan or rolling pin. Zest and quarter lemon. Halve zucchini lengthwise; slice crosswise into ¼-inch-thick half-moons. Peel and mince or grate garlic.

Heat a large drizzle of olive oil in a large pan over medium-high heat. Add panko, walnuts, and ¼ tsp oregano (½ tsp for 4 servings). (You’ll use more oregano in Step 6.) Toast, stirring, until golden and fragrant, 2-3 minutes.

Turn off heat; transfer walnut mixture to a small bowl. Season with ¼ tsp salt (½ tsp for 4) and pepper. Wipe out pan.

In a second small bowl, combine yogurt, sour cream, half the lemon zest, and a squeeze of lemon juice (use a big squeeze for 4 servings).

Add water 1 tsp at a time until mixture reaches a drizzling consistency. Season with salt and pepper.

Pat salmon* dry with paper towels; season all over with salt and pepper. Place, skin sides down, on a lightly oiled baking sheet. Top each piece of salmon with 1 tsp sauce; spread to coat evenly. Mound tops with walnut mixture, pressing to adhere (no need to coat the undersides).

Roast on top rack until salmon is opaque and cooked through, 8-10 minutes.

While salmon roasts, heat a large drizzle of oil in pan used for walnuts over medium-high heat. Add zucchini; cook, stirring occasionally, until softened and lightly browned, 5-7 minutes (7-10 minutes for 4 servings).

Add garlic, ¼ tsp oregano (½ tsp for 4), a big pinch of salt, and pepper. Cook, stirring, until fragrant, 1-2 minutes more. Taste and season with salt and pepper if desired.

Fluff rice with a fork; stir in half the scallion greens, remaining lemon zest, and a drizzle of olive oil. Season with salt and pepper.

Divide salmon, zucchini, and rice between plates. Drizzle sauce over salmon and sprinkle with remaining scallion greens. Serve with remaining lemon wedges on the side.