Prep the bread. Slice your bread and lightly toast it until the edges are crisp but the center is still soft. If you like a hint of garlic, rub the cut side with a peeled garlic clove right after toasting.
Season the tomatoes. Slice the tomatoes and lay them on a plate.
Sprinkle with a pinch of salt and pepper. Let them sit for 2–3 minutes to draw out extra sweetness and a bit of juice.
Layer the base carefully. Drizzle a little olive oil on the bottom slice of bread. If using pesto, spread a thin layer now.
This creates a barrier that helps prevent sogginess.
Add mozzarella. Lay down an even layer of mozzarella slices. Season lightly with salt and pepper. Good mozzarella loves a bit of seasoning.
Top with tomatoes and basil. Pat the tomato slices dry if they look very wet, then layer them over the mozzarella.
Tuck in whole basil leaves or torn pieces. Use plenty—basil carries a lot of the aroma.
Finish with flavor. Drizzle a small amount of olive oil and a few drops of balsamic or glaze over the tomatoes. Go light—too much liquid can make the sandwich messy.
Close and press. Place the top slice of bread on the sandwich.
Press gently with your palm to help everything nestle together. If you have time, let it sit for 2 minutes so the flavors mingle.
Slice and serve. Cut in halves or thirds with a sharp knife. Serve immediately while the bread is still crisp and the cheese cool and creamy.