Season diced tomatoes with kosher salt, then sit for 10 minutes.
Pulse onion, garlic, jalapeño, and cilantro in a food processor.
Add the chopped onion and pepper mixture to the diced tomatoes.
Toss chicken breasts with olive oil, garlic, salt, and pepper, then marinate for 30 minutes.
Grill the chicken breasts for 5-7 minutes per side.
Serve the grilled chicken on a plate with pico de gallo.