Add 2 tablespoons of the canola oil and the chopped onion to a skillet and sauté over medium heat until the onion is translucent, about 5 minutes, then transfer it to a small bowl and set aside.

Combine the tofu and potato starch in a bowl. Stir well to coat the tofu pieces completely.

Sauté the tofu in the remaining canola oil in the empty skillet until the tofu turns crispy and golden brown, about 5 minutes. Drizzle with the sesame oil and add the onion, then reduce the heat to low and add the teriyaki sauce. Mix well.

Divide the rice between two bowls and top with the tofu mixture. Drizzle with the mayonnaise, if using, and sprinkle with the sesame seeds and microgreens before serving.