Coat a 2-quart soufflé dish with cooking spray; sprinkle breadcrumbs over bottom and sides of dish.
Cook baby spinach in boiling water 15 seconds or until wilted, and drain in a sieve, pressing until barely moist. Finely chop; place in a large bowl.
Lightly spoon flour into a dry measuring cup; level with a knife. Place the flour, salt, ground nutmeg, ground red pepper, and black pepper in a medium saucepan. Gradually add milk, stirring with a whisk until blended. Bring to a boil over medium heat, stirring constantly. Cook 1 minute or until thick.
Gradually stir about one-fourth of hot milk mixture into egg yolk, stirring constantly with a whisk, and add to remaining hot milk mixture, stirring constantly. Cook 30 seconds, and remove from heat. Stir in baby spinach, cheese and dill. Cool slightly.
Place egg whites and cream of tartar in a large bowl, and beat with a mixer at high speed until stiff peaks form. Gently stir one-fourth of egg white mixture into baby spinach mixture; gently fold in remaining egg white mixture. Spoon into prepared soufflé dish. Bake at 350° for 45 minutes or until puffed, golden, and set. Serve immediately.