Pico de Gallo

4 roma tomatoes diced
1/2 white onion diced
1/2 bunch fresh cilantro finely chopped
1 fresh serrano pepper diced
1/2 tbsp. sugar
1/4 cup tomato paste
1/4 cup rice vinegar
kosher salt to taste
Mix sugar, tomato paste and vinegar in a bowl until smooth. 
Stir in remaining ingredients. Season with salt. Cover and 
chill to improve flavors. Serve with tortilla chips.