In a small bowl, mix gochujang, soy sauce, garlic, gochugaru, and sugar. Set aside.
In a large, shallow pot or pan, layer sliced onions across the bottom. Arrange tofu, Spam, bok choy, mushrooms, hot dogs, and kimchi neatly around the pot.
Pour in enough water or chicken broth to almost cover the ingredients. Place the ramen noodles in the center, on top.
Spoon the seasoning paste over the ingredients. Cover and bring to a boil over medium-high heat. Simmer for about 7–8 minutes, until the noodles are cooked and everything is heated through.
Place the slice of cheese on top. Cover for another 1–2 minutes, just until melted. Sprinkle with chopped green onions before serving.