In a small bowl, combine the pepper, coriander, smoked paprika, salt, brown sugar, garlic powder, onion powder and mustard powder. Rub the short ribs with the pastrami rub and let sit in the refrigerator, uncovered, at least 2 hours or up to overnight. The longer you can let them absorb the rub, the better the flavor will be.
Preheat the oven to 225 degrees F.
Place the ribs on a wire rack set in a baking sheet. Roast until the internal temperature reaches 200 to 203 degrees F and the ribs are fork-tender, about 4 hours. Serve with Braised Red Cabbage and Cranberry Mustard Sauce.
Braised Red Cabbage
In a large Dutch oven over medium-high heat, cook the bacon until crisp, about 5 minutes. Add the onions and season with about 1/2 teaspoon salt. Cook, stirring occasionally, until the onions are translucent, 7 to 8 minutes. Add the cabbage, apple, broth, apple juice, vinegar and granulated sugar. Season with 1/2 teaspoon each salt and pepper. Cover and cook until tender, about 45 minutes.
Cranberry 'Liquid Gold' Honey Mustard Sauce
Combine the mustard, honey, vinegar, cranberry juice, pepper and vanilla in a small pot and bring to a simmer, whisking constantly. Lightly simmer until the mustard sauce thickens, 6 to 8 minutes.