Return mushrooms to pot, and add Redpack Crushed Tomatoes, Redpack Diced Tomatoes, lentils, sugar, vinegar, basil, red pepper flakes and fennel. Bring to a simmer. Cover and allow to cook until lentils are tender but not mushy, about 35 minutes, uncovering and stirring occasionally. Remove cover and cook about 3 minutes more, stirring occasionally, until sauce thickens just a bit. Remove from heat. Season with salt and pepper to taste.