Wash and dry all produce. Preheat broiler to high or oven to 500 degrees. Halve zucchini lengthwise, then cut into long, thin wedges. Halve and peel onion, then cut into 1-inch-thick wedges. Finely mince 1 wedge. Zest lemon until you have 1 tsp zest, then cut into wedges. Halve tomatoes. Pick basil leaves from stems; discard stems. Thinly slice leaves.

Heat a drizzle of olive oil in a small pot over medium-high heat. Add minced onion and couscous. Cook, tossing, until onion is softened and couscous is lightly toasted, 2-3 minutes. Pour in 1 cup water and stock concentrate. Bring to a boil, then lower heat, reduce to a simmer, and cover. Cook until tender, 10-12 minutes.

Toss zucchini, onion wedges, sumac, and a large drizzle of olive oil on a baking sheet. Season with salt and pepper. Broil (or bake) until lightly charred, 10-15 minutes, tossing halfway through.

Heat a drizzle of olive oil in a large pan over medium-high heat (use a nonstick pan if you have one). Take 4 oz grilling cheese (about half the package; we sent more than needed) and cut into 2 large slices. Place za’atar on a plate. Press cheese into za’atar to evenly coat all over. Add to pan and cook until browned, 2-3 minutes per side.

Transfer couscous to a large bowl once done simmering. Stir in tomatoes, half the basil, a squeeze of lemon juice, and lemon zest. Season with salt and pepper.

Divide couscous between plates. Top with zucchini, onion, and grilling cheese. Garnish with remaining basil and serve with remaining lemon wedges on the side for squeezing over.