Preheat the oven to 375°F and line a large baking sheet with parchment paper.
Place the black beans in a food processor (fitted with the S blade) and pulse 5-7 times to break up the beans. Transfer to a large bowl and set aside. Scrape the sides of the processor container and be sure to get all the beans. You’re going to use the processor two more times.
Place the chopped carrot in the food processor and process for 20-30 seconds until the carrots are finely grated. Be careful not to over process. If the carrots are over processed they’ll start releasing liquid and become wet. Transfer the grated carrots to the bowl with the black beans.
Break the tempeh up until pieces and add to the processor and pulse until crumbly. Set aside.
Add the red onion to a medium sized non-stick sauté pan and sauté in a few tablespoons of water until they become translucent, about 5 minutes. Add water as needed to prevent burning. Add the garlic and all other spices and sauté for another 30 seconds.
Add the tempeh to the pan and continue to cook over medium heat for another few minutes, stirring often and adding water if needed to prevent burning.
Pour off any additional water from the tempeh/onion mixture and then add to the bowl with black beans and carrots. Add the tamari, buckwheat flour, nutritional yeast, and salt, and mix well using a spatula. Use the back of the spatula to press the mix together so it's nnice and sticky. The mix will be thick (see picture above).
Scoop out about ½ cup of the mix and shape firmly into a burger, keeping each burger at least 1 inch thick. Place on a baking sheet and repeat.
Place the baking sheet on the middle rack of the oven and bake for 25 minutes. Carefully flip using a spatula and bake for another 20-25 minutes. The burgers should be browned and firm to touch. Remove from the oven and let rest for at least 10 minutes. The burgers will firm as they cool. Serve with avocado, sauerkraut, sliced tomatoes and crispy lettuce and enjoy!