Pre-heat oven to 375°F or 190°C.
Roughly chop the onion, mushrooms, red pepper, and carrot. Add them to the blender and pulse until it becomes a chunky slurry.
In a large skillet, add the vegetable slurry with the minced garlic, salt and pepper and cook over medium heat until heated through (5-10 minutes). Set aside.
Meanwhile, in a food processor, pulse the lentils, oats, flax, bread crumbs, tomato paste, maple syrup, mustard, and parsley. It should be slightly chunky; do not over pulse. Add lentil mixture to the vegetable slurry and mix to combine and form a "dough."
Use a loaf pan lined with parchment paper. If you don’t have a loaf pan, you may form the dough into a loaf shape on a baking sheet. Place dough into the loaf pan, and gently press the top to form a bread shape on top. Bake for 40 minutes.
A few minutes before the 40 minutes are up mix together the basting ingredients in a small bowl. When the loaf is ready, drizzle the basting sauce on top and spread it around evenly. Return it to oven for an additional 10 minutes.
When it's done baking, remove from oven and let stand for 15 minutes before serving. Slice and enjoy!