Preheat oven to 450° F.
Cut potatoes in half lengthwise; add butter, garlic powder, and salt to each, then wrap in foil. (Cutting them in half will help them to cook faster). Bake for 30-35 minutes or until fork tender.
Dice cucumber.
In a small bowl, combine yogurt, cucumber, dill, and 2 tablespoons lemon juice. Add salt and pepper to taste, then set aside.
Place salmon onto a foil-lined baking dish and add to oven with the potatoes during the last 12-15 minutes of baking.
While fish and potatoes finish cooking, steam spinach; toss with olive oil and spritz with the remaining lemon juice.
Top salmon with the cucumber-yogurt sauce and serve with potatoes, spinach, and orange wedges on the side. (Serving size: 3ounces salmon, 1/2 orange, 1 potato, 1/4 cup spinach)