Mix flaxseed meal and water in a small bowl and place in the fridge for 5 minutes.
Place a large pan over medium heat and add 1 teaspoon of olive oil. Once oil is hot, add in onion, garlic and carrot; saute for 5 minutes or until onions are translucent and carrots begin to soften a bit. Transfer to a large bowl and stir in the spices: cumin, garlic powder, chili powder, paprika, salt and pepper.
Using a food processor or high powered blender, blend black beans until well blended and just a few bean chunks remain. Transfer to the bowl with the veggies and then stir in the flax egg and the oat flour. Taste, adjust seasonings and add additional salt and pepper if necessary.
Divide mixture into 4 patties. Put on a plate and cover with plastic wrap, place in the fridge for 10-15 minutes.
While the burgers are in the fridge firming up, make the garlic tahini sauce by mixing together the following in a small bowl: tahini, garlic, lemon juice, water and salt.
After 30 minutes, place a large skillet pan over medium heat and generously spray the pan with nonstick cooking spray. Add the patties and cook 4-5 minutes on each side, or until golden brown and heated through.
Place on buns with tomato, avocado, red onion and tahini sauce. Serve with sweet potato fries or a salad.