Slice the larger tomatoes into thick slices and halve or quarter the smaller ones. Place them onto a serving plate alternating color and sizes and sprinkle with the salt and pepper.
To make the dressing, in a large bowl, whisk together half the feta with the oil, vinegar, garlic and oregano until just combined. Season to taste with salt and pepper. Set aside.
Peel and slice the avocado and place it on top of the tomato. Top with the onion.
Pour the dressing over the salad.
Sprinkle with the remaining feta and serve.
Recipe Notes
Note: The dressing keeps well for up to 2 weeks in a jar in the refrigerator.