01 - Preheat oven to 350°F (175°C). Line a loaf pan with parchment paper, leaving overhang for easy removal.
02 - In a medium saucepan, combine lentils and vegetable broth. Bring to a boil, then reduce heat and simmer uncovered for 20 to 25 minutes, until lentils are tender and most of the liquid is absorbed. Drain any remaining liquid and set lentils aside.
03 - Heat olive oil in a skillet over medium heat. Add onion, garlic, carrot, celery, and red bell pepper; sauté for 6 to 8 minutes until vegetables are softened.
04 - In a large mixing bowl, mash cooked lentils with a fork or potato masher, leaving some portion textured.
05 - Add sautéed vegetables, rolled oats, walnuts (if using), ground flaxseed, tomato paste, soy sauce, balsamic vinegar, dried thyme, dried oregano, smoked paprika, black pepper, and salt to the lentils. Mix thoroughly until the mixture is fully combined. Allow to rest for 5 minutes so oats and flaxseed absorb moisture.
06 - Transfer the lentil mixture to the prepared loaf pan. Press mixture firmly into the pan and smooth the top with a spatula.
07 - In a small bowl, whisk together cranberry sauce, maple syrup, balsamic vinegar, and Dijon mustard until blended. Spread evenly over the top of the loaf.
08 - Bake in the center of the oven for 40 to 45 minutes until the loaf is firm and golden.
09 - Allow loaf to cool in the pan for at least 15 minutes before removing and slicing. Serve warm, optionally garnished with fresh herbs.