Place a grill pan or large skillet over medium heat and allow it to warm for 2–3 minutes. A properly heated pan helps the vegetables develop beautiful caramelization and prevents them from becoming soggy. If you're using a cast-iron grill pan, give it a little extra time to heat evenly. Avoid turning the heat too high, as this can burn the vegetables before they become tender.

While the pan heats, lightly brush both sides of the zucchini or eggplant slices with extra virgin olive oil. Sprinkle them evenly with minced garlic (or garlic powder), dried oregano, chopped fresh basil (if using), and freshly ground black pepper. The olive oil helps the seasonings adhere to the vegetables while promoting a rich, golden color during cooking.

Arrange the seasoned vegetable slices in a single layer in the hot grill pan. Cook them for 3–4 minutes on the first side without moving them too much, allowing light grill marks and caramelization to develop. Flip the vegetables carefully and cook for another 3–4 minutes, or until they are tender but still hold their shape. The vegetables should be soft enough to bite through easily while maintaining some texture rather than becoming mushy. Transfer them to a plate and set aside.

Lay the bread slices on a clean work surface. Using a pastry brush or the back of a spoon, lightly coat the outer sides of each slice with olive oil. You only need a thin layer to help the bread become golden and crisp during grilling. Too much oil can make the sandwich greasy instead of pleasantly crunchy.

Turn the bread slices over so the uncoated sides are facing up. Spread 1–2 tablespoons of hummus or olive oil-based pesto evenly across the inside of each slice. This creamy layer adds moisture, flavor, and helps hold the sandwich fillings together. Make sure to spread it all the way to the edges so every bite is flavorful.

Begin assembling the sandwich by layering the ingredients onto one slice of bread. Start with a handful of fresh spinach or arugula, followed by the grilled zucchini or eggplant. Add the roasted red peppers, tomato slices, and mozzarella or feta cheese. If you're using optional grilled chicken or salmon for extra protein, place it on top of the vegetables. Try to distribute the ingredients evenly so the sandwich stays balanced and easy to eat.

Place the second slice of bread on top of the fillings, making sure the olive oil-coated side faces outward. Gently press down on the sandwich with your hands to help hold everything together. Avoid pressing too firmly, as this can cause the fillings to spill out during cooking.

Reduce the heat slightly to medium-low and carefully transfer the assembled sandwich to the skillet or grill pan. Cook for 3–4 minutes on the first side, pressing gently with a spatula occasionally to encourage even browning and help the cheese soften. Flip the sandwich carefully and cook for another 3–4 minutes on the opposite side until the bread is crisp and golden brown and the cheese is warm and slightly melted. If the bread is browning too quickly, lower the heat to allow the inside to heat through properly.

Remove the sandwich from the skillet and place it on a cutting board or plate. Allow it to rest for 1–2 minutes before slicing. This brief resting period helps the cheese settle slightly and makes the sandwich easier to cut without the fillings sliding out.

Using a sharp knife, slice the sandwich in half diagonally for a classic café-style presentation. Serve it immediately while the bread is still warm and crispy and the vegetables are tender and flavorful. Pair it with a refreshing cucumber salad, a bowl of hearty lentil soup, or any Mediterranean-inspired side dish you enjoy for a complete and satisfying meal.