Preheat oven to 375 F Trim the brisket of most of its fat, and dust it very lightly with the flour. Sprinkle with pepper. Heat the oil in a large heavy flameproof casserole. Add the brisket, and brown on both sides over medium-high heat until some crisp spots appear on the surface. Transfer the brisket to a dish. Keeping the heat medium high, add the onions to the casserole and stir, scraping up the brown particles left from the meat. Cook until the onions have softened and developed a handsome brown color, 10 to 15 minutes. Remove the casserole from the heat, and place the brisket, along with any juices that have accumulated, on top of the onions. Spread the tomato paste over the brisket as if you were icing a cake. Sprinkle with pepper and the coarse salt. Add the garlic and carrot, and cover tightly. Place the casserole on the middle rack in the oven, and bake for 1-1/2 hours. Remove the casserole from the oven, and transfer the meat to a carving board. Cut it into 1/8 1/4 inch-thick slices. Return the slices to the pot, overlapping them at an angle so that you can see a bit of the top edge of each slice (in effect ressembling the brisket, slightly slanted). Correct the seasoning if necessary, and if absolutely necessary add 2 or 3 teaspoons of water to the casserole. Cover, and return the casserole to the oven. Cook until the meat is brown and fork-tender, 1-3/4 to 2 hours longer. Slice the carrot, and transfer the roast, onions and carrot slices to a heated platter. Serve at once.