Arugula, Mozzarella, Tomato on Focaccia

Ingredients

• 3 large tomatoes ripe cut into 1/4-inch-thick slices
• 1  onion red thinly sliced
• 3 tablespoons red-wine vinegar 
• 4 servings pepper black freshly ground
• 3 cups arugula packed trimmed coarsely chopped
• 4 servings focaccia bread halved for 4 sandwiches (enough )
• 0.5 pound mozzarella cheese fresh sliced thin ( is best)
• 1 Tbsp mayonnaise 

Equipment

• bowl
• baking pan

Directions

1. In a large bowl or baking dish combine tomatoes, onion, and vinegar and season with pepper and salt. Marinate 30 minutes.
2. Layer mozzarella, tomatoes, onions and arugula on the focaccia half.
3. Spread some mayonnaise on the top half of the focaccia if desired. Press top half over the bottom, hold together with a couple of tooth picks.