Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Press the extra firm tofu for at least 15 minutes to remove excess moisture, then cut into uniform 1-inch cubes.
Dice the Yukon gold potato into small 0.5-inch cubes so they roast at the same speed as the tofu.
In a large mixing bowl, whisk together the olive oil, nutritional yeast, garlic powder, onion powder, smoked paprika, sea salt, and black pepper.
Add the tofu and potatoes to the bowl and toss gently until every piece is thoroughly and evenly coated in the spice mixture.
Spread the tofu and potatoes in a single layer on the prepared baking sheet, ensuring they are not touching to allow for maximum crispiness.
Roast for 25 to 30 minutes, flipping the pieces halfway through, until the potatoes are tender and the tofu is golden and crisp.
During the final 2 minutes of roasting, scatter the baby spinach over the tray to let it lightly wilt from the residual heat.
Remove from the oven and serve immediately while the tofu and potatoes are at their peak crunch.