If you don't have a ready made basil pesto and you want to make your own homemade, start with it first. In a blender, blend the basil, garlic and nuts. Add the grated Parmesan cheese and blend. Gradually add olive oil while getting a thick paste.
The pesto is best used immediately, but can be stored in a tightly closed jar in the refrigerator and used for up to several days. If desired, it can be frozen in the freezer, but after unfreezing it is good to mix again with a little more olive oil.

To prepare the salad, cut the tomatoes into slices about 1 cm thick.
Cut the mozzarella into slices and place over the tomatoes. It is good to have a slice of mozzarella on each tomato piece.
With a small spoon, take some basil pesto and place over the mozzarella. Do not overdo it, because the taste of pesto is extremely rich. (You can replace the pesto with finely chopped fresh basil and sprinkle on top).

Finally season it. Sprinkle with salt, olive oil and, if desired, a little balsamic vinegar.