Preheat oven to 350°F.
Drain liquid from buckwheat and quinoa and pour into food processor.
Sauté onions, mushrooms, celery and garlic until the onions are translucent.
Add the cabbage to the pan with the onions and mushrooms and cook until cabbage is wilted, making sure all moisture is reabsorbed.
Pour into food processor along with remaining meatloaf ingredients and mix lightly.
Let sit for at least 15 minutes.
Add all tomato topping ingredients to a blender and blend until smooth.
Scoop meatloaf mixture into a parchment lined bread pan and smooth top.
Pour tomato topping mixture on top and smooth.
Bake for 1 hour.
Remove from oven and let cool for 15-20 minutes.
Remove meatloaf from pan and place onto a serving plate.
Will keep in the fridge in an airtight container for about 5 days.
