In a medium bowl, combine the chopped tomatoes, garlic, bell pepper, green onions, cilantro, jalapeño, lime juice, olive oil, and salt. Mix well, then cover and refrigerate for at least one hour to allow the flavors to blend. Taste and adjust seasoning if needed.
In a separate bowl, combine the ground beef, chopped onion, oregano, cumin, salt, and pepper. Mix until evenly combined, then shape into six equal patties about half an inch thick.
Preheat a grill or broiler. Cook the patties for about 5 to 7 minutes per side, or until they reach your preferred level of doneness.
To assemble, place a layer of tortilla chips in the center of each plate. Spoon a generous amount of the prepared salsa over the chips.
Add a layer of shredded lettuce on top, making it slightly larger than the burger patty.
Place a cooked burger on top of the lettuce. Add a spoonful of sour cream over each patty.
Finish with a sprinkle of fresh cilantro if desired, then serve immediately.