Preheat the oven to 375°F. Line a baking tray with parchment paper.
Prepare the flax egg: Mix 1 tablespoon ground flax meal with 2 ½ tablespoons warm water and let sit for 15 minutes to thicken.
Cook the onion and garlic. Heat a medium frying pan over medium heat with a touch of olive oil. Add the onions and cook for 3 minutes, until just starting to soften. Add the garlic and cook for another 1-2 minutes, until golden. Take off the heat.
Using your hands, crumble the tempeh (doesn’t need to be too finely crumbled).
Make the falafel dough. Add the crumbled tempeh to a food processor and pulse until it is finely broken down. Next, add the cilantro, parsley, basil, and walnuts and process until the ingredients start to blend together. Then, add the cooked onion and garlic, prepared flax egg, almond flour, 2 tablespoons olive oil, sesame seeds, salt, pepper to taste, cayenne pepper, cumin, coriander, turmeric, and baking soda. Blend until combined and the mixture sticks together.
Place the dough in the refrigerator for 20 minutes. Otherwise, it will be sticky and more difficult to handle.
Spoon the refrigerated dough into approximately 22 falafel balls (one heaping tablespoon of dough for each). Place the falafel on the prepared baking tray and bake in the preheated oven for 20-22 minutes, turning halfway through baking time, until browned on both sides.