Boil water and blanch green beans for 3-4 minutes, then cool under cold water.
Prepare hard-boiled eggs by boiling for 9-12 minutes, then place in ice water.
In a large bowl, combine mixed salad greens and cherry tomatoes.
Add blanched green beans to the salad mixture and toss gently.
Layer tuna over the salad, breaking it into chunks.
Arrange quartered hard-boiled eggs on top of the salad.
Sprinkle black olives and sliced red onion over the salad.
In a small bowl, whisk together olive oil, red wine vinegar, salt, and pepper.
Drizzle the dressing over the salad just before serving.
Serve immediately and enjoy!