For the pickled onions, add the thinly sliced red onion, apple cider vinegar, salt, and pepper to a jar. Affix the lid, then shake to mix the ingredients. Store in the fridge for at least 30 minutes or up to overnight.
Preheat the oven to 375°F. Toss the potatoes in the olive oil and sprinkle with the salt and pepper. Roast for 40 minutes, or until just starting to brown.
Make the buffalo sauce by combining the hot pepper sauce and butter. Then, season the chicken with the salt and pepper, toss with the buffalo sauce, and when the sweet potatoes have 25 minutes of baking left, add the chicken tenders to the oven to bake at 375°F for those 25 minutes, then roughly shred with two forks.
While the sweet potatoes and chicken cook, make the ranch dressing. Add the Greek yogurt, mayonnaise, lemon juice, dried dill, garlic, and salt to a bowl and whisk until combined.
Plate with an even amount of the quinoa, potatoes, chicken, carrots, avocado, pickled onions, and chives across 4 bowls - garnish with the additional salt, pepper, buffalo sauce, and ranch dressing as you like.