Get ready. Preheat the oven to 400°F. Fill a large 9x13-inch baking dish with the baby spinach, and lay the leaves in an even layer. The spinach will seem to be too much, but remember, it will shrink as it cooks.
Make the glaze. In a small bowl, add the pomegranate molasses, olive oil, lime zest and juice, cinnamon, red pepper flakes (optional), and salt. Mix well until uniform.
Glaze the salmon. Place the salmon fillets on the bed of spinach, evenly spaced out. With a spoon or a brush, spread the glaze all over the salmon, generously. If you have any of the glaze leftover, pour it over the spinach, around the salmon fillets.
Bake the salmon. Place your baking sheet/dish in the oven and bake for 15 minutes, or until the salmon is flaky, and cooked all the way through. The glaze will have darkened and caramelized. The spinach will have shrunk and cooked down into a saucy vegetable accompaniment for the salmon. Serve immediately.