Preheat an electric panini maker according to the manufacturer’s instructions.
Step 2
Brush one side of each bread slice with olive oil.
Step 3
Lay the slices, oiled side down, on a clean work surface.
Step 4
Spread the top of each slice with mayonnaise.
Step 5
Place the turkey on one slice and top with the bell pepper, cheese and watercress. Season with salt and pepper.
Step 6
Top with the other bread slice, oiled side up.
Step 7
Place the sandwich on the preheated panini maker and cook according to the manufacturer’s instructions until the bread is golden and the cheese is melted, 3 to 5 minutes.
Step 8
Transfer the sandwich to a cutting board and cut in half.