How to Make It
Put the couscous in a large heatproof bowl. In a medium saucepan, heat 2 tablespoons of the olive oil until shimmering. Add the shallots, sage and a generous pinch each of salt and pepper. Cook over moderate heat, stirring, until softened, 5 minutes. Add the water, the grapefruit, orange and lime juices and 2 tablespoons of the lemon juice. Season with salt. Bring to a boil and stir in the citrus zests. Pour the liquid over the couscous, cover with plastic wrap and let stand at room temperature until the liquid is absorbed, 20 minutes. Fluff with a fork. Fold in the remaining 1/3 cup of olive oil and 1/4 cup of lemon juice. Season with salt and pepper and serve.