On a microwave-safe plate or bowl add onions, celery and cook for 3 minutes to soften.
In a large nonstick pot or pan, add the chopped pastrami and saute over medium high heat, stirring often, for 1 minute. Add garlic and softened onions and celery. Continue to cook for 2 minutes, stir often. Add vinegar and deglaze the pot with vinegar; cook until nearly evaporated, about 1 minute.
Stir in beef broth, ketchup, mustard, relish, paprika, cabbage and black pepper; bring to a boil. Reduce heat, cover and simmer for 15 minutes, until cabbage is crisp-tender.