Press the tofu for about 30 minutes to remove excess moisture.
Whisk the vinegar, oil, tamari, mustard, syrup, and garlic powder (or fresh garlic) together.
Cut the tofu into cubes. I use a method similar to this, and I end up with 32 cubes total. Place the tofu cubes into a glass lock or another storage container that has a lid. Pour the marinade over them. Cover the container, shake it to coat all of the tofu cubes, and allow the tofu to marinate for at least two hours or up to overnight. Refrigerate the tofu if you marinate it for longer than two hours.
Preheat your oven to 425F. Line a baking sheet with parchment or foil.
Transfer the tofu cubes to the baking sheet. Reserve the marinade in case you need extra for basting the tofu as it bakes; I usually don’t, but I like to keep it handy.
Bake the tofu cubes for 15 minutes. Flip them around on the baking sheet. The cubes should look darkened and have a glazed appearance at this point, but if they look at all dry or pale, you can brush them with the extra, reserved marinade.
Return the cubes to the oven and bake for another 15-20 minutes, until the cubes are darkened and becoming crisp. Serve or store.