Mix the soy sauce or tamari and apple cider vinegar in a bowl until well combined.

Incorporate the tofu cubes and let marinate for at least 5 minutes.

Drain the tofu and transfer ⅓ of the tofu cubes to a freezer bag with 2 tablespoon of cornstarch and toss to coat. Repeat this step with all the remaining tofu and cornstarch. Add more cornstarch if needed.

Heat half of the oil in a skillet and when it’s hot, add the tofu cubes. Cook over medium-high heat until all sides are golden brown. Remove the tofu from the skillet and set it aside.

Heat the other half of the oil in the skillet and when it’s hot, incorporate the veggies (carrot, green bell pepper, red bell pepper, and onion). Cook over medium-high heat until golden brown. Set aside.

To make the sauce just mix all the ingredients until well combined.

Pour the sauce into the skillet and cook until it thickens, stirring frequently.

Mix the tofu, veggies, and the sauce in the skillet, stir, and cook for about 5 minutes over medium heat, stirring occasionally.

Serve your sweet and sour tofu immediately with some sesame seeds on top (optional).

Keep the leftovers in a sealed container in the fridge for up to 1 week.