Preheat the oven to 500 degrees. Put the pepper on a flat plate. Place a large skillet, preferably non-stick, over medium-high heat; add the olive oil. Dredge both sides of each piece of tuna lightly in the pepper; it will adhere nicely, forming a thin coat. (Use a bit more pepper if necessary.).
As they're dredged, add the steaks to the pan. Turn the heat to high. Cook about 2 minutes, then turn. Add salt and cook 1 more minute. Turn heat to low and remove tuna to an ovenproof plate. Place in oven.
Add half the butter to the pan, followed by the shallots. Lower the heat to medium and cook, stirring, until the shallots soften, about 2 minutes. Raise the heat to medium-high and add the wine; let it bubble away for a minute or so and add the remaining butter. Cook, stirring occasionally, until the butter melts and the sauce is thickened.
By this time the tuna will be medium-rare (cut into one to make certain). Cut the steaks in half, put each serving on a plate, and spoon a little sauce over it.