Combine tomatoes and 1/8 tsp. kosher salt in a large bowl. Let stand 5 minutes. Add basil leaves, olive oil, balsamic vinegar, pepper, 1/4 tsp. kosher salt, and mozzarella; toss.
I used sliced heirlooms in place of the cherry tomatoes as that is what my garden had to offer. You really can't go wrong with a Caprese salad.