Seared Tuna with Olive Tapenade

2 tuna steak, about 6 oz each, 1-inch thick

2 tbsp olive oil

1 tsp kosher salt

½ tsp black pepper, freshly ground

¾ cup kalamata olives, pitted and roughly chopped

¼ cup green olives, pitted and roughly chopped

2 tbsp capers, drained and rinsed

2 anchovy fillet, minced

1 shallot, finely chopped

1 clove garlic, minced

2 tbsp flat-leaf parsley, finely chopped

2 tbsp lemon juice, freshly squeezed

1 tsp lemon zest, finely grated

1 tsp red wine vinegar

2 tbsp extra-virgin olive oil

¼ tsp crushed red pepper

4 cup mixed greens, for serving (optional)