Preheat your oven to 400°F and line a baking sheet with parchment paper.
Trim the Brussels sprouts and halve them, then toss with half of the avocado oil and a pinch of salt on the prepared sheet.
Season the pork tenderloin evenly on all sides with sea salt, black pepper, and garlic powder.
Heat a cast-iron or oven-safe skillet over medium-high heat with the remaining avocado oil and sear the pork for 2 minutes per side until a golden crust forms.
In a small bowl, whisk together the honey, tamari, and Dijon mustard until the glaze is smooth and combined.
Brush half of the honey glaze over the top of the pork and transfer the skillet to the oven alongside the Brussels sprouts.
Roast for 12 to 15 minutes, brushing with the remaining glaze halfway through, until the pork reaches an internal temperature of 145°F.
Remove from the oven and let the pork rest for 5 minutes before slicing to ensure the juices redistribute for a tender finish.