Season chicken breasts with salt, pepper, garlic salt, and onion powder.
Add olive oil to pan and place chicken breasts in pan. Cook until golden brown, about 5 minutes and flip breasts. Place pan in oven until chicken is cooked through, reading 165 degrees Fahrenheit internally with a thermometer, about 20-25 minutes. Remove pan from oven, and place chicken breasts on a plate to cool. Chill overnight in an airtight container, or in the fridge for 1-2 hours.
Pull apart chicken breasts into large pieces with two forks, and set in a large mixing bowl.
Top chicken with blueberries, celery, onion, and pistachios.
In a small mixing bowl, whisk mayo, yogurt, vinegar, lemon juice, and zest. Pour sauce mixture over chicken and gently mix together. Season to taste with salt and black pepper.
Serve over a mixed greens salad or on a roll with sliced tomato and lettuce.