Heirloom tomatoes got their name due to the way they are grown. Unlike regular tomatoes they are open-pollinated, meaning they grow directly from the seed of a previous fruit whose variety has been around for at least 50 years. The tomatoes themselves are delicate and can't take too much handling so they are typically picked and sold within two days making them the freshest tomatoes you can find. The skin is incredibly tender and they are quite absorbent so they work quite nicely with vinaigrettes in salads.
1 1/2 tablespoons balsamic vinegar
3/4 teaspoon salt
1/4 teaspoon black pepper
1/4 cup olive or vegetable oil
3 pounds mixed heirloom tomatoes, halved if small or cut into slices if medium or large, cut carefully so as not to bruise the skin
Chopped fresh basil
Sliced fresh mozzarella
Whisk together vinegar, salt, and peper in a large bowl. Add oil in a slow, continuous stream, whisking constantly until both parts oil and vinegar are emulsified. Add tomatoes and mozzarella, gently toss to coat. Season with salt and pepper to taste.