Slice the ciabatta into 6 pieces that are big enough for 1 person to eat. Then slice it in half width-wise so that there is a top and a bottom to the sandwich.
On the bottom slice of bread, add 2 slices of mozzarella, then tomato slices. Season with salt and pepper, and then drizzle on some olive oil.
Next, place on the basil leaf or chiffonade basil and then the top slice of bread. This is the most traditional way to prepare and serve a caprese sandwich.
You can optionally add balsamic reduction and pesto to further enhance the sandwich's flavor.
Notes
Fresh summer tomatoes make this meal, but using cold tomatoes is one of the most common mistakes I see when someone puts a tomato-and-mozzarella sandwich together. Cold temperatures actually dull a tomato’s flavor and give it a mealy texture. That’s why I recommend storing your tomatoes at room temperature and waiting to slice them until right before assembling for the best results.Don’t season the sliced tomatoes too soon, like when they’re still on the cutting board. The salt will cause them to release their sweet juices way before they reach the sandwich. Seasoning them while they’re on the bread draws out their natural juices at the perfect moment, creating an instant dressing with the olive oil.When my ciabatta is too soft, I’ll toast the sliced halves under the broiler for a minute or two before making the sandwich. If you’re craving a hot caprese panini instead, drizzle the outer crust with olive oil and place the assembled sandwiches in a hot cast-iron skillet or panini press. Cook until the bread turns golden brown and the mozzarella is nice and gooey.No peak-season tomatoes?Oven-roasted tomatoes, slow-cooked tomato confit, or marinated sun-dried tomatoes are your best options when fresh tomatoes are out of season.To make this tomato basil sandwich even more filling, try layering on thin slices of prosciutto or a juicy chicken breast. Or, to keep it vegetarian, add sliced avocado, roasted red peppers, or a handful of fresh arugula or baby spinach. Make-Ahead: The sandwich is best served right away. If you want to pack it up for work or a picnic, I recommend storing the bread, sliced cheese, and basil in separate containers and slicing the tomatoes right before assembling the sandwich.How to Store: Cover the leftovers and refrigerate them for up to 1 day.