In a medium skillet, over medium heat, add the olive oil. Stir in the onions, carrots, garlic slices, and red pepper flakes. Season with salt, to taste, and cook for about 2 minutes. Add the sugar and the canned tomatoes, breaking them up with a spoon, and mix well. Cook for an additional 10 to 15 minutes over medium heat, stirring from time to time. Taste for seasoning, then stir in the basil leaves.