Tuna Smothered In Onions And Mint   3 Tablespoons Olive Oil 3 Large Yellow Onion -- thinly sliced 1 1/2 Pounds Tuna Steak Salt And Pepper -- to taste Flour -- for dredging 4 Tablespoons Vegetable Oil 5 Tablespoons Wine Vinegar 1 Tablespoon Honey 8 Sprigs Mint -- torn Ground White Pepper -- to taste  Prepare dish one day in advance. In heavy skillet over medium heat, place oil, onions and 1 cup water. Bring to boil. Stirring occasionally until water has evaporated about 25 minutes. Season tuna with salt and pepper. Dust with flour. Fry in vegetable oil for 2 minutes per side. Transfer to platter. Add to skillet vinegar, honey and 1/2 cup water. Cook and stir for 30 seconds until liquid is reduced by half. Pour over onions, raise heat to high and carmelize onions. Remove from heat, season with salt and pepper and cool until lukewarm. Season tuna with salt, pepper and mint. Pour onions and juices over the top. Cool, cover and refrigerate overnight. To serve. Remove wilted mint leaves. Correct seasonings and reheat in 400 degree oven for 10 minutes.