How to Make It
Preheat a water bath to 122° for rare salmon, 160° for medium. Light a grill or preheat a grill pan. Season the sliced cucumber with salt and black pepper. Grill over high heat, turning once, until lightly charred, about 2 minutes. Transfer to a plate.
Season the salmon with salt and white pepper; transfer to four 1-quart, vacuum-pack bags and vacuum-seal. Submerge the bags in the water bath and cook at the desired temperature for 12 minutes.
In a blender, blend the yogurt with the dill; season with salt and black pepper. In a small bowl, toss the julienned cucumber with the oil and lemon juice; season with salt. Remove the fillets from the bags and transfer to plates. Top with the grilled and julienned cucumber, dollop with the dill sauce and serve.