Season the chicken breast evenly with garlic powder, 0.125 tsp sea salt, and 0.125 tsp black pepper.
Grill the chicken over medium-high heat for 6-7 minutes per side until the internal temperature reaches 165°F, then let it rest before slicing into thin strips.
Place the pepitas in a small dry skillet over medium heat and toast for 2-3 minutes, stirring constantly until they are fragrant and golden brown.
Chop the romaine lettuce into bite-sized pieces, slice the cucumber into half-moons, and thinly slice the radishes.
In a small jar or bowl, whisk together the lime juice, extra virgin olive oil, and the remaining sea salt and black pepper to create the dressing.
In a large salad bowl, combine the romaine, cucumber, and radishes; toss thoroughly with the prepared dressing.
Top the salad with the sliced grilled chicken, half of a sliced avocado, and the toasted pepitas.