Heat oil in a large frying pan on medium. Cook garlic and onion for 5 minutes, until softened. Remove and set aside. Add tuna steaks to same pan and brown for 1 minute on each side. Return onion and garlic to pan with wine and tomato paste. Stir and season to taste.
Reduce heat to low, cover and simmer gently for 3 minutes. Stir through peas, until heated through. Serve immediately.