Preheat oven to 400°F. Line a baking sheet with parchment paper.
Combine the quinoa with 1 1/2 cups water in a small saucepan and bring to a boil. Reduce the heat, add garlic powder, stir, cover and simmer for 10 to 15 minutes, or until all the water is absorbed. Transfer to a mixing bowl and let cool slightly.
Prepare the flax egg by combining 2 tablespoons ground flax meal with 3 tablespoons water in a bowl. Whisk, then place in the fridge while you prepare the rest of your ingredients.
Steam spinach for 4-5 minutes over 1-2 inches of simmering water. Remove from heat, reserving the water to boil your potato. Rinse spinach with cold water, then squeeze dry. Finely chop the spinach, then add it to the bowl of quinoa.
Add the onion, garlic, flax egg, potato, flour, baking powder, salt, cumin, and pepper to the bowl of quinoa/spinach. Mix well to combine.
Shape into 10 patties and place on the prepared baking sheet.
Bake for 15 minutes, flip them over, then bake for another 10 minutes, until golden brown and firm.
While the patties are baking, prepare your sauce. Combine tahini, water, lemon juice, salt and garlic powder in bowl. Whisk, then pour into a jar so you can store leftovers.
To assemble, place quinoa burger patty in a whole wheat burger bun, add your favourite fresh toppings and pour lemon tahini sauce overtop.