1/2 cup mayonnaise
3 tablespoons ketchup
2 tablespoons finely chopped dill pickle
Kosher salt and freshly ground pepper
3 cups grated Swiss cheese (about 9 ounces)
2/3 cup sauerkraut, drained, rinsed and roughly chopped
4 ounces cream cheese, at room temperature
4 ounces chopped sliced pastrami (about 1 cup)
1 round or oval loaf pumpernickel bread (about 8 inches)
Extra-virgin olive oil, for drizzling
Crackers and/or crudites, for serving