Combine garlic powder, paprika, salt, and pepper in a small bowl. Place chicken breasts between plastic wrap and pound to 3/4-inch even thickness. Rub the seasoning mixture thoroughly over both sides of each breast.

Heat olive oil in a large skillet over medium-high heat. Add chicken breasts and cook undisturbed for 6-8 minutes until golden-brown, then flip and cook another 6-8 minutes until internal temperature reaches 165°F.

Transfer cooked chicken to a cutting board and let rest for 5 minutes. In a small bowl, whisk together olive oil, lemon juice, Dijon mustard, minced garlic, honey, salt, and pepper until smooth.

Slice the rested chicken against the grain into 1/2-inch strips. In a large mixing bowl, combine mixed greens, cherry tomatoes, cucumber, bell pepper, red onion, and sunflower seeds.

Pour dressing over the salad and toss gently. Divide salad among four bowls, top each with sliced chicken and fresh avocado slices. Serve immediately.