Gazpacho Sandwich

Name: Gazpacho Sandwich
Ingredients: 2 teaspoons Dijon mustard; 2 tablespoons sherry vinegar or apple cider vinegar; 3 tablespoons good-quality extra-virgin olive oil; 1/8 teaspoon kosher salt; 1/8 teaspoon freshly ground black pepper; 1 shallot (chopped 1/2 cup crumbled feta cheese); 1 round sourdough (sliced into 1/3-inch slices); 3 or 4 ripe tomatoes (thinly sliced); 1/4 teaspoon kosher salt; 1 medium cucumber or 1/2 of an English cucumber (peeled and thinly sliced); 1 yellow bell pepper (cored, seeded, and sliced into thin strips); 2 cups arugula; 1/4 cup cilantro leaves (roughly chopped); 1/4 cup basil leaves (roughly chopped); 1/4 teaspoon freshly ground black pepper