Preheat your oven to 375°F (190°C).
Prepare Flax Eggs:
In a small bowl, mix flaxseed meal with water and let it sit for about 5 minutes to form a gel-like consistency.
Prepare the Loaf:
In a pan, sauté the chopped onion and garlic in olive oil until softened.
Add chopped mushrooms and cook until they release their moisture and become golden brown.
In a food processor, combine black beans, sautéed mushroom mixture, rolled oats, flax eggs, soy sauce, rosemary, salt, and pepper. Pulse until well combined but still slightly chunky.
Form the Loaf:
Transfer the mixture to a greased loaf pan, pressing it down firmly.
Smooth the top with a spatula.
Prepare the Glaze:
In a small bowl, whisk together tomato paste, maple syrup, balsamic vinegar, Dijon mustard, salt, and pepper.
Glaze and Bake:
Spread the glaze over the top of the loaf.
Bake in the preheated oven for 40-45 minutes or until the loaf is firm and golden brown.
Serve:
Allow the loaf to cool for a few minutes before slicing.
Serve slices with additional glaze on the side if desired.