Heat a saucepan on the stove over medium heat, add the coconut aminos, orange juice, rice vinegar, garlic, ginger and red chili flakes to the pan, whisk to combine.

Bring to a boil, then simmer 4-5 minutes.

In a small bowl, combine the tapioca starch and water, add this to the boiling sauce and whisk together.

Reduce the heat to low and simmer 3-4 minutes.

Remove the teriyaki sauce from the heat and set aside to cool.

Preheat the oven to 400°F.

Place the pork tenderloin in a large baking dish, slice the pork every ½ inch ¾ of the way through, then add a slice of pineapple in between each slice of pork.

Add the bell pepper and onion to the dish around the pork.

Spoon the teriyaki sauce over the pork and pineapple.

Drizzle the coconut oil over the bell peppers and onions.

Place in the oven and roast for 15 minutes, remove from the oven, cover with foil and continue cooking for 15-20 minutes, or until a thermometer inserted in the middle of the pork reads 140°F.