In a large bowl, toss all ingredients together and store in the refrigerator for a couple of hours before serving.
To serve as a hot salad:
To serve this as a hot side dish, simply take a couple of tablespoons of the olive oil and add to a sauté pan.
Add the onions; sauté, over medium heat, until they soften a little.
Add the olives and tomatoes to the pan and sauté for another couple of minutes just to warm them through.
Remove from heat; toss with all remaining ingredients; serve.
Notes
One caution when seasoning this salad is not to go overboard with the salt. Since the olives are quite salty, this will need little or no additional salt added.