Beef sandwich on a bun

Ingredients:

• 6 Kaiser rolls
• 700 gr. beef brisket, cut into slices
• 1 red onion, thinly sliced ​​into half rings
• 1 tbsp. salt plus 2 tsp. and additional to taste
• 6 tablespoons red wine vinegar
• 3/4 cup mayonnaise
• 3/4 cup sour cream
• 1/4 cup plus 2 tablespoons preserved grated horseradish (with liquid)
• 1/2 tsp grated lemon zest
• Hot sauce
• 12 tomatoes on a branch
• 3 cups watercress and arugula mixture

Preparation:

1. In a small bowl, combine the onion and 1 tablespoon of salt. Set aside for 20 minutes. Rinse the onion under cold running water and gently squeeze to remove excess liquid. Combine the onion and vinegar and marinate for at least 30 minutes or up to 24 hours.
2. In a small bowl, combine mayonnaise, sour cream, horseradish, zest and 2 teaspoons salt. Season generously with pepper and hot sauce to taste. Refrigerate the horseradish sauce for at least 30 minutes.
3. Preheat the broiler. Cut the buns in half lengthwise. Use your hands to make a shallow indentation in each half. Transfer the buns, indented side up, to a baking sheet. Toast the bread in the broiler for about 1 minute.
4. Spread a thick layer of sauce on the inside of each bun. On the bottom half of each bun. Kaiser rolls Place 2 slices of tomato, season with salt and pepper to taste. Top with a few overlapping slices of beef, season with salt and pepper. Top with some onion and watercress and cover with the top half of the bun. Serve immediately.
   
   Recipe baked beef sandwiches and a sauce of mayonnaise and horseradish.