Whisk together olive oil, lime zest and juice, cumin, minced garlic, salt and pepper. Set aside. If preparing ahead of time, store in an airtight container. Can sit out at room temperature up to 2 hours, otherwise store in the fridge and let come to room temp when ready to use.
In a large bowl, combine black beans, corn, cilantro, tomatoes and red onion. Cover tightly and store until ready to serve.
Just before serving, Pour dressing over the salad and toss to coat. Gently stir in diced avocado.
All of the ingredients amounts are approximate - feel free to use more or less or omit any of them you like.