In a skillet large enough to hold all the snap peas, sauté the pancetta over a moderate flame until its fat is well rendered and it is beginning to brown nicely. Add the shallots or fresh onions and let it sauté as well, until translucent.
Add the tomatoes to the skillet and let them sauté until they just begin to melt, then add in the snap pea and give them a good turn so they are well covered with the pancetta and tomato.
Sauté the snap peas, turning frequently, until they are done to your liking, as little as 5 minutes if they like them crisp tender and up to 15 if you prefer them "well done". There should be a small amount of sauce clinging to them. You may need add water along the way if things dry out too much.
Serve right away.
Cherry tomatoes can be subbed with small Campari style tomatoes, cut into cubes.