Mix together vinegar, honey, greek yogurt, mustard, onion powder, garlic powder, and red pepper flakes. Let sit for 15 minutes.
Toss bread pieces in olive oil. Toast in skillet until crispy. Set aside.
Pat salmon dry and season salmon with salt. Place salmon in a cold cast iron pan. Heat on a camp stove to medium heat. Cook for 4-5 minutes until the skin easily releases from the pan. Flip and cook flesh side down for 2 minutes. Remove from pan and set aside.
Toss ferns, lettuce, onion, dill, and walnuts in the dressing. Stir in bread. Divide salad between 4 plates. Top with a filet of salmon and serve.