Preheat the oven to 375 degrees F.
Combine the lemon juice, 1 Tbsp. orange juice, 2 Tbsp. olive oil, oregano, cumin, salt and pepper in a medium bowl. Add the cucumber, orange and onion and toss to combine. Cover and refrigerate until needed.
Place the salmon on a non-stick or parchment paper-lined baking pan. Drizzle with the 1 Tbsp. olive oil and 2 Tbsp. orange juice; season with salt and pepper. Bake 15 minutes, or until cooked through. Set a piece of salmon on each of 4 plates and serve the salad alongside.