Season the steak on all sides with salt, pepper, and half the pastrami spice blend. Let sit 15-20 minutes.

Halve, peel, and thinly slice the onion. Peel and grate the carrot. Pick the dill fronds from the stems.

Braise the cabbage: Heat 1 tablespoon oil in a large pan over medium heat. Add the onion and cabbage to the pan and cook, tossing 4-5 minutes, until softened. Add the carrot, stock concentrate, and 1 cup water to the pan. Bring to a simmer and cook 12-15 minutes, until liquid has evaporated and vegetables are very soft. Add half the white wine vinegar to the pan. Season with salt, pepper, and the remaining pastrami spice blend (to taste). Keep on the stove over low heat to stay warm.

Cook the steak: in another large pan, heat 1 teaspoon oil over medium-high heat. Add the steak to the pan and sear 4-7 minutes per side, until cooked to desired doneness. Set steak aside to rest for 5 minutes.

Make the pan sauce: heat the same pan over medium heat. Add the remaining white wine vinegar and scrape up any browned bits from the bottom of the pan. Remove the pan from the heat and stir in the1 tablespoon ketchup and 2 tablespoons mayonnaise. Season with salt and pepper.

Slice the steak against the grain, then serve on a bed of cabbage. Spoon the pan sauce over the steak and garnish with dill fronds.