Place the tuna steaks into a shallow bowl and add the honey, soy sauce and garlic, turning the steaks over to coat them with the marinade then leave for 5 minutes.
Blanch the runner beans for 5 minutes, then refresh under cold water and place in a bowl. Add the butterbeans, red onion, shredded basil, 1 tbsp of the olive oil and lemon juice to the bean salad and mix well.
Heat the remaining olive oil in a pan and cook the tuna steaks for 5-6 minutes on either side. Serve the tuna steaks with the bean salad.