01 - Preheat a grill or grill pan over medium heat.
02 - Brush both sides of the eggplant slices with olive oil and season with salt and pepper.
03 - Grill eggplant slices for 4–5 minutes per side until tender and grill marks appear.
04 - Lightly toast the sandwich rolls on the grill for 1–2 minutes if desired.
05 - Spread hummus or pesto on the bottom halves of each roll.
06 - Layer grilled eggplant, tomato slices, arugula, mozzarella cheese (if using), and red onion.
07 - Top with the other half of the roll, press lightly, and serve warm.