Pat the chicken breast cubes dry with a paper towel and toss in a medium bowl with sea salt, black pepper, and arrowroot starch until every piece is thoroughly coated.
In a small glass jar or bowl, whisk together the coconut aminos, rice vinegar, honey, and tomato paste until the sauce is smooth and combined.
Heat the avocado oil in a large cast-iron skillet or wok over medium-high heat until the oil is shimmering and hot.
Add the chicken to the skillet in a single layer, leaving space between pieces, and sear for 3-4 minutes per side until they develop a deep golden-brown crust and are cooked through.
Remove the crispy chicken from the pan and set it aside on a plate.
Using the remaining oil in the pan, add the chopped bell peppers, minced garlic, and grated ginger, sautéing for about 3 minutes until the peppers are tender yet still vibrant.
Stir in the pineapple chunks and the prepared sweet and sour sauce, allowing the liquid to bubble and thicken for 1 minute.
Return the crispy chicken to the skillet and toss quickly for 30 seconds to glaze the meat without losing the crunch, then serve immediately.