Cook the quinoa in salted water or broth according to package instructions. After it's cooked season the quinoa with additional salt, pepper and half the lemon juice. Reserve the other half of the lemon for garnish.
Assemble the bowl by putting the quinoa and spinach on the bottom of the bowl as a base. Then add the cucumbers, tomatoes and sliced red onions. Add the hummus and lemon. Drizzle with the lemon tahini dressing!