In a large bowl, combine the chopped tomatoes, sliced red onion, minced garlic, and torn basil leaves.
In a separate bowl, whisk together the olive oil, red wine vinegar, sea salt, black pepper, and crushed red pepper flakes (if using).
Drizzle the dressing over the tomato and onion mixture and gently fold everything together until evenly coated.
Allow the salad to rest for about 15 minutes at room temperature to enhance the flavors.
Serve the salad chilled or at room temperature, adding extra basil on top for presentation.