Wash the vine-ripe tomatoes under cold water. Cut each in half and scoop out the seeds. Dice the tomatoes into small pieces and set aside in a mixing bowl.

Finely dice a red onion and soak in cold water for 5-10 minutes if necessary. Drain and combine with the diced tomatoes.

Rinse fresh cilantro, shake off excess moisture, and finely chop the leaves. Add to the mixing bowl.

Zest and juice the limes into the bowl. This step adds brightness and acidity.

Sprinkle sea salt over the mixture, toss gently, and adjust seasoning if necessary just before serving.