Step 1Steam halibut in steamer basket over simmering water until fish flakes easily when tested with fork, about 10 minutes. Let halibut cool to room temperature and serve, or cover and chill up to 2 days.
Step 2Seed 1/2 cucumber, then mince. Combine minced cucumber, yogurt, garlic, dill and salt. Cover and chill until ready to assemble salad.
Step 3Divide greens between 2 serving plates. Slice remaining 1/2 cucumber and arrange around greens. Spoon rice over greens. Remove any skin and bones from fish and flake fish. Arrange on top of rice and surround salad with tomato wedges. Spoon dressing over salads.