In a medium bowl, combine the yogurt, cucumber, carrot and 1 tablespoon lemon juice; season with salt.
In a large nonstick skillet, heat the olive oil over medium-high heat. Season the tilapia with the paprika, curry powder, salt and pepper. Add to the skillet and cook, turning once, until just cooked through, about 5 minutes. Drizzle with the remaining lemon juice. Serve with the cucumber salad and top both with the scallion.