1. Heat the olive oil in a large skillet and saute the onion and garlic for 2 minutes.
2. Add the tuna steaks and sear them on both sides, approximately 1 minute per side.
3. Remove the tuna steaks from the skillet and set them aside.
4. Add the red peppers, celery and olives and saute for 3 minutes more.
5. Deglaze with the white wine, add the pomodoro sauce and season to taste.
6. Reduce the sauce slightly and return the tuna steaks to the skillet.
7. Put the skillet in a preheated oven and bake for about 8-10 minutes or until the desired doneness.
8. Boil the penne according to taste and toss it with some of the Mediterranean sauce.
If you don't have a skillet with oven-proof handle, use a baking pan instead.