In a small bowl or dish, mix the marinade ingredients (4 tbsp of tamari and 2 tbsp of apple cider vinegar), stir to mix.
Place the tofu cubes in the marinade and turn to coat. Allow to marinate at least 5 minutes. For a deeper flavor, let marinate overnight in your refrigerator.
Drain the tofu and discard the marinade.
Put the cornstarch in a separate dish. Add the tofu cubes and turn gently to coat each piece. If needed, add more cornstarch.
Heat the oil in a wok or skillet to medium-high temperature.
Add the tofu cubes and cook until all sides are golden brown. Be careful not to turn the pieces until they are browned. Turning more frequently results in mushy cubes, rather than the desired texture. Remove the tofu from the skillet and set aside.
Add the garlic to the skillet (add more oil if needed) and cook over medium-high heat for about 1 to 2 minutes, stirring frequently until golden brown. Set aside.
Mix all the sauce ingredients in a bowl (tamari or soy sauce, apple cider vinegar, vegetable stock or water, sweetener, cornstarch and red pepper flakes).
Add the sauce to the wok or skillet that you cooked garlic in. Cook, stirring constantly, over medium-high heat until it thickens, about 2-3 minutes.
Now, add the tofu cubes. Stir and cook for 1 to 2 more minutes.
Garnish with sesame seeds. Serve with vegetable of your choice and brown rice.
Keep leftovers in an airtight container in the fridge for up to 5 days.