Whisk together the oil, vinegar, oregano, and garlic cloves.
Trim the chicken breasts and gently pound them to uniform thickness.
Place the chicken in a dish that's at least 2 inches thick (I use an oval baking dish), and pour the marinade over the chicken. Turn the chicken to coat it. Cover and allow to marinate for 2 hours or up to 2 days in the fridge.
Make the Hummus: While the chicken marinates, make the hummus. Soak the sunflower seeds in warm water for 30 minutes, then drain. Add all ingredients to a blender or food processor and blend until smooth. If need be, thin by blending in a little extra oil until it's the desired consistency. It should be creamy and spreadable, but not too thick.
Cook the chicken: Heat 2 tbsp oil in a large skillet over medium heat. Season the chicken lightly with salt and pepper, and add them to the skillet. Cook for about 5 minutes per side, turning once (10 minutes total). Remove them from the skillet and allow to rest a few minutes before cutting.
Assemble the salad: Divide the lettuce between four bowls. Top with sliced chicken, hummus, pickled onions, and sun dried tomatoes, and a sprinkle of oregano and salt and pepper, and serve.
Notes
Note: I find the salad does not need dressing because the hummus and the oil from the tomatoes works nicely together. If you'd like to add a salad dressing, a drizzle of balsamic oil and vinegar would work great!