Season the chicken
Pat chicken dry. Season both sides with garlic powder, salt, paprika, and black pepper.
Cook the chicken
Heat olive oil in a skillet over medium heat. Cook chicken for 6 to 7 minutes per side, or until golden brown and the internal temperature reaches 165 degrees Fahrenheit. Transfer chicken to a plate and allow it to cool completely.
Cook the vegetables
Reduce heat to medium low. Add celery and red onion to the same pan. Saute for about 5 minutes, until softened and aromatic. Season with a small pinch of salt. Transfer vegetables to a bowl and let cool.
Make the dressing
In a large mixing bowl, combine mayo, Dijon mustard, red wine vinegar, red pepper flakes, and dill. Mix until smooth. Stir in walnuts, dried cranberries, cherry peppers, cherries, and pickles.
Assemble
Once chicken has cooled, cut into small cubes. Add chicken, cooled vegetables, and white cheddar cubes to the bowl. Toss until evenly coated. Taste and adjust salt and pepper as needed.