Prepare the tomatoes by cutting larger heirloom tomatoes into thick wedges and halving cherry tomatoes. Place them in a large glass bowl.

Slice the red onion thinly and soak in cold water for five minutes if desired. Drain and add to the bowl with the tomatoes.

Stack basil leaves, roll tightly, and slice into thin ribbons (chiffonade). Roughly chop parsley and finely mince mint. Add all herbs to the bowl.

In a small jar or bowl, whisk together olive oil, red wine vinegar, sea salt, and black pepper until slightly thickened. Pour over the salad and toss gently.

Let the salad sit at room temperature for at least ten minutes before serving to allow flavors to meld.