Whisk 2 tbsp olive oil, 2.5 tbsp lemon juice, garlic, oregano, paprika, 1 tsp salt, pepper, and red pepper flakes.
Add chicken and coat well. Marinate 15–30 minutes while you make the salsa. Reserve remaining lemon juice and oil.
Combine tomatoes, cucumber, olives, red onion, parsley, feta, remaining lemon juice, a drizzle of olive oil, vinegar, and zest. Season with a pinch of salt.
Heat a large skillet over medium-high. Add a thin film of olive oil and sear chicken 5–6 minutes per side until 165°F.
Rest chicken 5 minutes, slice, and plate. Spoon feta salsa over the top and serve.