Heat a 10-inch saute pan over medium heat, and add the olive oil. When the oil is hot but not smoking, add the shallots and garlic and cook for about 1 minute. Add the tomatoes and cook, stirring often, for an additional minute. Deglaze the pan with the wine and reduce until nearly evaporated, about 4 minutes. Add the capers and lemon juice to the pan, and swirl the butter into the sauce a little at a time until all the butter is incorporated. Add the chopped parsley to the sauce and season with salt and pepper. Remove the sauce from the pan and reserve until the fish is grilled.
Set a grill or a grill pan over medium-high heat and season with vegetable oil. Season the tuna with the salt and pepper. Once the grill is hot, place the tuna on the grill and sear for 2 minutes. Turn the tuna over and cook for an additional minute for rare, or 2 minutes for medium. Serve the tuna with the sauce draped over 1 side of the fish and falling onto the plate. Garnish with sprigs of fresh parsley.
Yield: 4 servings