Combine diced tomatoes, onion, jalapeños, and cilantro in a large bowl.
Add garlic powder, lime juice, vinegar, sugar, salt, pepper, and red pepper flakes.
Mix well and taste. Adjust seasonings as needed.
Let rest for 15–30 minutes before serving for best flavor.
Store leftovers in an airtight container in the fridge for up to 3 days.