Slice your tomatoes, and either cut the mozzarella into slices or tear the mozzarella.
Spread a layer of pesto on one half of the panini bread, and top that half with your sliced tomatoes. On the other half of your bread, lay down a bed of basil, and top that with your mozzarella.
Bring both the bread halves of the panini together. If you have a panini press, paninis generally take around 5-7 minutes in the press before they are ready to enjoy hot. However, if you don’t have a panini press, don’t worry. Instead, place your assembled paninis in a hot pan, and press them with a heavy object, like a large cooking pot.
Keep them pressed until you can see the cheese has melted, by which point they should be hot and ready to serve. You don’t have to be too precious with it, and if they’re still not quite ready, simply place them back in the pan and press down again for a little while longer.