Preheat the oven to 350F. Pat salmon dry with paper towels, then place on a parchment lined baking sheet.
Place extra virgin olive oil, red wine vinegar, fresh lemon juice, grated garlic clove, Kosher salt, dried oregano, and black pepper in a mason jar. Seal the lid tightly, shake well, then pour on top of the salmon filet. Place a few fresh dill sprigs on top.
Place in a preheated oven and bake for 12-15 minutes, depending on how thick the salmon is. The internal temperature should reach 120F. While the salmon cooks, make the salad.
Place thinly sliced red onion in a small bowl with red wine vinegar. Allow this to sit while you make the salad. In a large mixing bowl, combine tomatoes, diced cucumbers, cubed feta cheese, and halved Kalamata olives.
Drain the red onion (you can reserve the red wine vinegar for another use), then add to the bowl with the salad ingredients. Drizzle with extra virgin olive oil, the reserved red wine vinegar, dried oregano, Kosher salt, and a pinch of black pepper. Toss.
When the salmon is finished, spoon the horiatiki salad on top. Enjoy immediately with lemon wedges and additional fresh dill!