I used diced pickled beets, if you use whole pickled beets cut them into small dice. Drain beets well and coarsely chop. Add scallions and radishes and set aside.
In a small bowl combine the yogurt, Feta, parsley and oregano. Stir in ¼ teaspoon of kosher salt and a pinch of black pepper. Set aside.
Cut salmon into roughly 2½ inch squares that are about ½ inch thick. Slice thick parts of the filet in half to make thinner if needed. Cut 12 portions.
Sprinkle filets with salt on both sides. Coat filets evenly with blackened seasoning.
Heat a nonstick skillet or cast iron pan over medium to medium-high heat and add 2 tablespoons oil. Add the salmon, in batches if needed, and cook, turning once, until salmon is crisped and almost cooked through, about 1½ minutes per side. Remove and let rest.
Spread slider buns with yogurt sauce. Layer arugula, salmon and beet relish on each slider and serve.
• Nutrition facts are a close calculated estimate based on the weight of the ingredients. *To make ¼ cup of your own Blacked Seasoning Blend, combine 2 tablespoons smoked paprika, ½ teaspoon cayenne, 2 teaspoons garlic powder, 1½ teaspoons oregano and 1 teaspoon ground black pepper.