Add the cubed tofu, tamari/soy sauce, oil and garlic powder to a large bowl, mix until well combined and let the tofu marinade for at least 5 minutes.
Drain the tofu, transfer 1/3 of the tofu cubes to a freezer bag with 1 or 2 tbsp of cornstarch and toss to coat. Repeat with the rest of the tofu cubesand cornstarch.
Place the tofu cubes onto a lined baking sheet and then bake them for 30 minutes or until golden brown, flipping the tofu cubes halfway.
Serve immediately or keep leftovers for 4 to 5 days in an airtight container in the fridge.