Seen this on the PBS show Test Kitchen. Tried it and it was great!
From TK website:
"Heat varies from jalapeño to jalapeño, and because much of the heat resides in the seeds, we suggest mincing the seeds separately from the flesh, then adding minced seeds to taste. The amount of sugar and lime juice to use depends on the ripeness of the tomatoes. The salsa can be made 2 to 3 hours in advance, but hold off adding the salt, lime juice, and sugar until just before serving. The salsa is perfect for tortilla chips, but it's also a nice accompaniment to grilled steaks, chicken, and fish.
Makes about 3 cups.