- Halve the potatoes lengthwise. Roughly chop red leaf lettuce and pull butter lettuce apart. Trim and quarter radishes. Halve tomatoes, thinly slice red onion, and cut cucumbers into half moons.
- Add juice, zest, vinegar, garlic, oregano, 1/2 teaspoon salt, pepper, olive oil and feta to a blender. Blend until smooth. Refrigerate until ready to use.
- Add the potatoes to a medium pot of salted water. Bring to a boil over medium-high heat. Boil until tender, about 10 minutes. Drain and run under cold water until the potatoes are room temperature. Pat them dry and set aside.
- When you are ready to assemble your salad, layer the bottom of the platter with both types of lettuce. Arrange the remaining ingredients in sections. Pour the dressing over and serve immediately.