Season the chicken breast evenly on both sides with sea salt, black pepper, and dried oregano.
Heat 0.5 teaspoon of olive oil in a medium skillet over medium-high heat.
Place the chicken in the skillet and cook for 6-7 minutes per side, or until the internal temperature reaches 165°F and the exterior is golden brown.
While the chicken is cooking, prepare the dressing by whisking together the extra virgin olive oil, lemon juice, and Dijon mustard in a small bowl.
In a large salad bowl, combine the mixed baby greens, sliced cucumber, halved cherry tomatoes, and thinly sliced radishes.
Once the chicken is finished, let it rest for 3 minutes before slicing it into thin strips.
Arrange the sliced chicken on top of the greens, then add the sliced avocado and sprinkle with pumpkin seeds.
Drizzle the lemon vinaigrette over the salad just before serving and toss gently to combine.