If using Roma tomatoes, cut in half lengthwise and gently squeeze them over a bowl to remove the seeds and pulp. There's no need to de-seed cherry tomatoes.
Finely dice the tomatoes, jalapeño, onion and cilantro and add to a medium bowl.
Add the lime and salt and toss to combine.
Allow to sit at room temperature for 30 minutes or so before eating. Best if eaten the same day but can be made two or three hours ahead if needed.