Remove from heat and place tomato olive mixture in a large heat-proof bowl. Wipe out the fry pan and add the remaining EVOO. Heat up the pan until it starts to smoke and add the tuna steaks. Sear for 1-2 minutes per side. The tuna should not be cooked all the way through. It should be deep red in the middle.
Add the tomato-olive mixture to the pan, along with the chopped parsley and heat through, coating the tuna with the mixture to absorb the flavors.
Slice the tuna into 1/8" slices, place on a platter with the tomato-olive mixture and serve.