How to Make It
Combine celery, bell peppers, and lemon juice in a medium bowl. Stir in 1/4 teaspoon salt and 1/4 teaspoon black pepper. Let stand at room temperature 10 minutes. Toss with cilantro.
Meanwhile, stir together butter, ketchup, and hot sauce in a large bowl.
Heat oil in a large nonstick skillet over medium-high. Add chicken, and cook until lightly browned on all sides, 3 to 4 minutes. Sprinkle with remaining 1/4 teaspoon salt and remaining 1/4 teaspoon black pepper. Add chicken to hot sauce mixture; toss to coat.
Stir together sour cream and blue cheese. To assemble tacos, spread 1 1/2 teaspoons of the sour cream mixture on each tortilla. Divide chicken and celery mixture evenly among tortillas; top with cilantro and hot sauce.