In a shallow bowl, whisk together soy sauce, lemon juice, maple syrup, sriracha, and garlic powder. Add the tofu and toss gently to coat, arranging the tofu in a single layer in the bowl. Let marinate 15-20 minutes, flipping the tofu once.
Transfer the tofu to a zip top freezer bag, discarding any leftover marinade. Add cornstarch to the bag one tablespoon at a time, zipping it up and shaking around to coat the tofu entirely. You have enough when there’s a thin white layer of cornstarch covering the tofu.
Heat coconut oil in a large cast iron skillet over medium heat. Once hot, add the tofu and cook 2-3 minutes per side until golden and crispy.