How to Make It
In a bowl, whisk the lemon juice and harissa with 2 tablespoons of the olive oil. Add the fennel, celery and orange slices, season with salt and pepper and toss. Transfer the salad to plates.
In a large skillet, heat the remaining 1 tablespoon of olive oil until smoking. Season the shrimp with salt and pepper and add to the skillet. Cook, stirring once, until just pink and curled, about 2 minutes. Transfer the shrimp to a plate.
Add the grapefruit juice to the skillet and cook until reduced by half. Swirl in the butter, then add the chives and shrimp; simmer for 2 minutes, stirring. Top the salad with the shrimp and serve.