In a bowl, whisk together gochujang, rice vinegar, soy sauce, garlic, and ginger until smooth.
Add salmon cubes and toss to coat evenly in the sauce.
Heat the rice according to package instructions and set aside.
Heat oil in a non-stick pan over high heat.
Add salmon pieces and cook quickly, turning to sear all sides.
Pour remaining sauce into the pan and stir briefly.
Cook until salmon is just done and tender.
Assemble bowls with rice, salmon, cucumber, and kimchi.
Sprinkle with sesame seeds if desired. These Spicy Salmon Rice Bowls are best served warm.