Bring juice, stock, 1 tablespoon of oil, vinegar, 1⁄2 TL sugar, salt and pepper to the boil in a pot. Put the couscous in a bowl. Pour the tomato stock over it. Cover and let it swell for about 5 minutes.
Preheat oven (electric cooker: 220 °C/circulating air: 200 °C/gas: see manufacturer). Wash the tomatoes and cut them crosswise into slices. Wash basil and shake dry. Pluck off the leaves. Roughly pluck the mozzarella.
Grease an ovenproof dish (approx. 17 x 28 cm) with oil. Loosen up the couscous and 1⁄3 Spread the couscous in the dish, press lightly. Spread each 1⁄3 tomatoes, cheese and basil on top. Repeat until all ingredients are used up, finishing with cheese. Sprinkle with 1 tablespoon of olive oil. Bake in a hot oven for about 20 minutes.