How to Make It
In a large, shallow glass or ceramic dish, combine the chopped cilantro with the coriander seeds, wine and 2 tablespoons of the olive oil. Add the tuna steaks and turn to coat. Refrigerate for at least 1 hour or overnight.
Preheat the broiler. Put the bell peppers in a baking pan and broil until charred all over. Transfer the peppers to a bowl, cover with plastic wrap and let steam for 10 minutes. Working over the bowl, peel, core and seed the peppers, then quarter them lengthwise. Return the peppers and their juices to the bowl, add the remaining 1 tablespoon of olive oil and season with salt and pepper.
Light a grill or preheat a grill pan. Remove the tuna from the dish and scrape off most of the marinade. Season the tuna with salt and pepper and grill over a hot fire or over high heat until charred on both sides and rare inside, about 3 minutes per side.
Slice the tuna across the grain and arrange on 6 plates. Serve 2 pieces of roasted pepper per person. Sprinkle a few drops of soy sauce over each serving and garnish with cilantro sprigs.