Authentic Pico de Gallo

Bahan-bahan (6 porsi)

• 1 lb Roma tomatoes ((3-4 medium), or garden tomatoes, diced)
• 1/2 medium white onion ((1 cup chopped), or yellow onion or red onion)
• 1 jalapeno pepper (seeded and finely minced (optional))
• 1/2 cup cilantro (chopped)
• 2 Tbsp lime juice (from 1 lime)
• 1/2 tsp salt (or to taste)
• 1/8 tsp black pepper