Lightly dust brisket with flour; sprinkle with pepper. In a Dutch oven, brown brisket in oil on broth sides over medium-high heat. Remove and keep warm. In the drippings, saute onions until golden brown, about 15 minutes. Return meat to pan. Combine tomato paste, salt and garlic; spoon over meat.
Cover and bake at 375° for 1-1/2 hours. Slice meat across the grain; return to pan, overlapping slices. Add carrots. Cover and bake 1-1/4 to 1-3/4 hours longer or until meat is tender.