Place a large, deep sauté pan over medium-high heat. Place ¼ cup oil in pan and add thyme, fennel, and onion; salt to taste. Sauté for 5 minutes. Add peppers and garlic and cook for 2 minutes. Add wine; boil until reduced by half. Remove from heat and add parsley, chives, mint, and basil. Add tomatoes and citrus zests. Season with salt and set aside to let flavors marry.
Salt and pepper tuna; coat heavily with fennel pollen. Place a medium sauté pan on high heat. When pan is very hot, add a little oil, and then sear fish on all sides until crispy. (Use two pans, if necessary, to avoid crowding fish, and be careful not to overcook.)
Divide pepper mixture (piperade) among four shallow bowls. Top with a little arugula. Place fish on top and enjoy immediately.