Whisk together the gochujang, tamari, toasted sesame oil, minced garlic, and grated fresh ginger in a small bowl to create the glaze.
Thinly slice the cucumber and toss with rice vinegar and sea salt in a side dish; allow to sit and quick-pickle while cooking.
Finely dice the pork belly and add it to a large skillet over medium-high heat, cooking until the fat renders and the pieces are crispy.
Cube the pork tenderloin into bite-sized pieces, add to the skillet with the pork belly, season with black pepper, and sear until browned.
Pour the gochujang glaze over the pork mixture and stir constantly for 2 minutes until the sauce reduces into a thick, glossy coating.
Steam or sauté the cauliflower rice in a separate pan until tender and heated through, then divide into serving bowls.
Top the cauliflower rice with the spicy pork mixture, add the pickled cucumbers on the side, and garnish with sliced green onions.