Wash and dry produce.

Trim and thinly slice scallions, separating whites from greens. Halve tomatoes lengthwise. Trim and quarter cucumber lengthwise; slice crosswise into ½-inch pieces. Zest and quarter lemon. Peel and mince or grate garlic. Finely chop dill.

Heat a drizzle of olive oil in a small pot over medium-high heat. Add scallion whites; cook, stirring, until fragrant, 30 seconds. Stir in couscous, stock concentrate, ¾ cup water (1½ cups for 4 servings), and a big pinch of salt. Bring to a boil, then cover and reduce heat to low. Cook until tender, 6-8 minutes. Keep covered off heat until ready to serve.

Meanwhile, in a small bowl, combine tomatoes, cucumber, half the scallion greens, and half the Greek vinaigrette (all for 4 servings). Season with salt and pepper.

In a second small bowl, combine yogurt, sour cream, juice from one lemon wedge (two wedges for 4 servings), a large drizzle of olive oil, a pinch of garlic, and as much dill as you like. Add water 1 tsp at a time until sauce reaches a drizzling consistency. Season with salt and pepper.

Rinse shrimp* under cold water and pat dry with paper towels.

Heat a large drizzle of olive oil in a large pan over medium-high heat. Add shrimp, oregano, remaining garlic, salt, and pepper. Cook, stirring, until opaque and cooked through, 4-6 minutes.

Remove pan from heat; stir in lemon zest and juice from remaining lemon wedges.

Stir remaining scallion greens and a drizzle of olive oil into pot with couscous; season with salt and pepper.

Divide couscous between bowls; top with shrimp and salad. Drizzle with sauce and serve.