In a shallow bowl, whisk together soy sauce, coconut sugar, garlic powder, rice vinegar, and toasted sesame oil until smooth. Set aside some marinade for glazing later.

Cut the tofu into cubes and marinate at room temperature for 30 minutes.

Combine reserved marinade with arrowroot powder and water in a saucepan, simmer until thickened.

Preheat grill to medium-high heat and thread marinated tofu and red onion onto skewers.

Grease the grill with avocado oil, grill skewers for 10-15 minutes, turning occasionally.

Brush skewers with teriyaki glaze before removing from grill, garnish and serve.