Melt butter over medium high heat. Reduce heat to medium and add bell pepper, celery and onions and cook about 5-7 minutes, adding garlic in the last 30 seconds to 1 minute.
Stir in flour and salt, stirring to keep it smooth. Cook, stirring constantly until the sauce is lightly browned. This should take about 7-8 minutes.
Add shrimp, stock, lemon juice and seasoning. Cook, stirring until shrimp are done - about 5-6 minutes
Stir in green onion and parsley, reserving a little if desired for garnish.
Serve over rice.
