Steak Sandwiches

Meanwhile, halve, peel, and thinly slice the red onion. In a small bowl, combine the sour cream with 1 teaspoon mustard (or to taste), horseradish powder, and a pinch of salt and pepper. Set aside.

Heat ½ tablespoon olive oil in a medium pan over medium heat. Season the steak with salt and pepper on both sides. Sear the steak for 6-7 minutes per side, until browned and cooked to desired doneness. Remove from the pan and set aside for 5 minutes to rest.

While the steak breasts, add the red onion to the same pan you cooked the teak in. Cook, tossing, over the medium heat for about 5 minutes, until softened. Stir half the watercress and half the balsamic vinegar into the onions and cook for about 1 minute, until watercress is slightly wilted. Season with salt and pepper. Meanwhile, halve each ciabatta and place them on the baking sheet in the oven to toast for about 5 minutes.

Remove the baking sheet from the oven. Thinly slice the steak against the grain. In the medium bowl, toss the remaining watercress with ½ tablespoon olive oil, remaining balsamic, roasted tomatoes, salt, and pepper.