Combine water and salt in a saucepan; bring to a boil. Remove from heat. Add couscous; stir well. Cover and let stand 5 minutes or until couscous is tender and liquid is absorbed. Add black beans and next 5 ingredients; stir gently.
Combine ricotta cheese, vinegar, oil, and cumin; stir into couscous mixture. Spoon mixture into an 11x7x2" baking dish coated with cooking spray. Bake, uncovered, at 350F for 25 minutes or until thoroughly heated.
Cut spinach leaves into thin strips. Place 1 cup spinach on each serving plate; spoon couscous mixture evenly over spinach.
Nutritional Analysis (per serving): Calories 299, protein 15.3g, fat 5.8g, carbo 47.4g, sodium 206g, cholesterol 13mg