Rinse the quinoa thoroughly in a fine-mesh strainer and combine with 0.5 cup water in a small pot.
Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes until the water is absorbed and the quinoa is fluffy.
Press the tofu for 10 minutes to remove excess moisture, then cut into 1-inch cubes.
In a bowl, toss the tofu cubes with nutritional yeast, garlic powder, and half of the sea salt until evenly coated.
Heat olive oil in a non-stick skillet over medium-high heat and add the sliced mushrooms, sautéing until they release their moisture and turn golden brown.
Add the seasoned tofu to the skillet and cook for 8-10 minutes, turning occasionally, until the edges are crispy and browned.
Prepare the dressing by whisking together the tahini, lemon juice, gluten-free tamari, and the remaining sea salt in a small jar until smooth.
Shred the cabbage, chop the romaine lettuce, and grate the carrot to create a fresh vegetable base.
Assemble the power bowl by placing a bed of lettuce and cabbage at the bottom, followed by the cooked quinoa and grated carrots.
Top with the warm pan-seared tofu and mushrooms, then drizzle the lemon-tahini dressing over the entire bowl before serving.