Slice the pork tenderloin into small, bite-sized cubes to mimic the texture of pork belly.
In a small bowl, whisk together the gochujang, tamari, honey, garlic powder, and ginger powder to create the glaze.
Heat the sesame oil in a large skillet over medium-high heat until shimmering.
Add the pork cubes to the skillet and sear until browned and crispy on all sides, approximately 5 to 6 minutes.
Pour the spicy glaze over the pork and toss to coat, cooking for another 2 minutes until the sauce becomes thick and sticky.
In the final minute of cooking, add the fresh spinach to the pan and toss just until wilted.
Assemble the bowl by placing the warm cooked brown rice at the base.
Top the rice with the glazed pork, wilted spinach, fresh cucumber slices, and tangy kimchi.
Garnish the entire bowl with sesame seeds and serve immediately.