Preheat the oven to 425°F (220°C). A high oven will quickly roast the tomatoes and gently cook the cod without drying it; the hot air concentrates tomato sweetness and gives the fish a short, precise cook.

Toss the cherry tomatoes with 1 tbsp olive oil, half the minced garlic (1 clove), 1/4 tsp kosher salt and a pinch of black pepper in a small baking dish or rimmed sheet tray. Spread them in a single layer so they blister evenly. Roasting at high heat concentrates their sugars and intensifies umami — the result is a sweet, slightly smoky tomato sauce for the couscous.

Drizzle the cod fillets with 1 tbsp olive oil and season both sides with 1/2 tsp kosher salt and 1/4 tsp freshly ground pepper. Zest half the lemon over the fish for fragrant citrus oils that brighten the cod. Seasoning just before cooking keeps the flesh tender and allows the lemon zest to sit on the surface where you taste it immediately.

Place the baking dish with tomatoes on the middle rack and roast for 10 minutes. After 10 minutes, push the tomatoes to one side of the dish and place the cod fillets skin-side down (if skin-on) or presentation-side up on the other side. Return to the oven and roast an additional 8–10 minutes, until the cod is opaque through the center and flakes easily with a fork (internal temperature about 145°F/63°C). Timing at high heat keeps the fish moist and lets the tomatoes blister without turning to complete mush.

While the tomatoes begin roasting, bring 1 1/4 cups water (or broth) to a boil in a small saucepan. Stir in a pinch of salt (about 1/8 tsp). Using boiling liquid seals the surface of couscous quickly and yields light, separate grains.

Optional but recommended: warm 1 tsp olive oil in a small, dry skillet over medium heat and briefly toast the dry couscous for 1 minute, stirring — you’ll smell a faint nutty aroma. Toasting blooms the grain’s oils and adds depth that plain steamed couscous lacks.

Place the couscous in a small heatproof bowl or the saucepan, pour the boiling water/broth over it, stir once to combine, cover tightly, and remove from heat. Let it rest, covered, for 5 minutes — this standard steam step hydrates the grains evenly so they’re tender but not gummy.

Fluff the couscous with a fork to separate the grains. Add the remaining 1 tbsp olive oil, the remaining minced garlic, lemon juice (about 2 tbsp from the lemon), chopped basil (reserve a few whole leaves for garnish), and a pinch of salt and pepper. Toss gently — the oil and lemon juice coat the grains, adding shine and carrying flavor.

When the cod is done, remove the baking tray from the oven. Use a spoon to break some of the roasted tomatoes so their juices mingle — this creates a quick pan sauce. Let the cod rest 2 minutes; resting allows carryover cooking to finish the fish without overcooking and lets juices redistribute.

To plate: mound a generous half of the lemon-basil couscous on each plate, spoon the roasted tomatoes and their juices over the couscous, and top with a cod fillet. Finish with a drizzle of the remaining 1 tbsp olive oil (for gloss and mouthfeel), a few torn basil leaves, a little lemon zest, and freshly ground black pepper to taste.

Taste and adjust seasoning — a quick squeeze of lemon at the table or a pinch more salt will lift the dish. Serve immediately so the fish remains warm and the couscous stays light and fluffy.