Preheat oven to 400°F.
Rinse quinoa under cold water; combine with water or broth in a pot. Bring to a boil, then simmer covered for 15 minutes until water is absorbed. Fluff with a fork.
Place salmon fillets on a baking sheet lined with parchment. Drizzle 1 tbsp olive oil over salmon.
Mix lemon zest, thyme, parsley, salt, and pepper in a small bowl; spread evenly over each fillet.
Bake salmon for 12-15 minutes until cooked through and flaky.
Meanwhile, heat remaining 1 tbsp olive oil in a large pan over medium heat. Sauté garlic for 1 minute until fragrant.
Add spinach and cook until wilted, about 3-4 minutes. Season with salt, pepper, and optional red pepper flakes.
Serve baked salmon over a bed of quinoa and sautéed spinach. Drizzle lemon juice over the top before serving.