1. In a skillet or wok, stir-fry asparagus in oil until crisp-tender.
2. Remove and keep warm.
3. In the same skillet, stir-fry red pepper, walnuts, ginger, garlic, and pepper flakes for 2 minutes or until red pepper is crisp-tender.
4. Stir in water, soy sauce, sugar, and salt; heat through.
5. Add asparagus; stir to coat.