Dice the onion and soak in cold water for about 20 minutes. This will help reduce that strong oniony taste. To make the chopping process faster I love using a vegetable chopper.
Pour the onions and water into a mesh strainer and let the water drain out.
With a tomato corer or knife, remove the cores of each tomato. Cut each tomato in half and dice using a chopper or sharp knife. I prefer using a chopper because it's a lot faster.
Dice the jalapeños and cilantro. Make sure to wash your hands very well after touching the jalapeños. Or better yet use gloves instead!
In a large bowl, combine the diced tomatoes, onions, jalapeños, and cilantro. Mix in salt and lime juice. You can add more salt or jalapeños depending on how salty or spicy you like your Pico de gallo. I usually add a little more salt when using homegrown tomatoes because they tend to be a lot sweeter than the store-bought ones.