1 teaspoon seasoned salt (such as Spice Islands® Beau Monde Seasoning)
freshly ground black pepper to taste
2 1/2 cups shredded Swiss cheese, divided
1 (6 ounce) package rye croutons
Cook and stir onion, celery, red bell pepper, butter, garlic, tarragon, and caraway seeds in a stock pot over medium heat until vegetables are tender, 6 to 8 minutes.
Slowly stir flour into vegetable mixture. Cook on low until flour is lightly browned, stirring constantly, about 10 minutes.
Stir beef stock, half-and-half, corned beef, sauerkraut, seasoned salt, and black pepper into vegetable mixture. Reduce heat to low and simmer until soup is heated through and slightly thickened, about 30 minutes.
Stir 2 cups Swiss cheese into soup until melted. Ladle soup into individual bowls and top with rye croutons and remaining Swiss cheese.