Stir together all ingredients except tomatoes and avocados in a large mixing bowl.
Add tomatoes to bowl.
Cut avocado in half and remove pit. Dice flesh and add to bowl. Gently mix. Serve immediately.
Notes
The amount of salt needed depends on the amount already in the black beans.Make Ahead Tip: Mix together all ingredients except tomatoes and avocados and place in a sealed container in the refrigerator. Add tomatoes and avocados immediately before serving.Variation: Add 1 bell pepper, seeded and diced, along with the tomatoes and avocado.