Preheat the oven to 375°F (190°C) and line a sheet pan with parchment paper.

Place salmon on the prepared sheet pan and allow to come to room temperature. Stir melted butter and orange juice together in a small bowl, and brush on salmon fillets. Season with salt and pepper.

Bake salmon in the preheated oven until an instant read thermometer, inserted near the center, reaches 145°F (63°C), about 13 to 15 minutes.

Meanwhile, for drizzle, combine pomegranate juice, brown sugar, orange juice, and salt in a small saucepan over medium-high heat. Bring to a boil, and cook, stirring frequently, until the mixture is slightly thickened, about 10 minutes. Remove from heat.

For spinach, pour olive oil into a large skillet, and heat over medium heat until oil shimmers. Add garlic and cook, stirring, until garlic is fragrant, about 30 seconds. Add spinach and cook, turning and stirring, until just wilted and still bright green, about 2 minutes.