Cook the kimchi in a large skillet over low to medium heat until soft (about 5 minutes), stirring frequently.
Add the yellow onions, gochugaru, soy sauce, gochujang and minced garlic to the skillet and stir to combine. Cook over medium heat, stirring frequently for about 3 minutes.
Add the broth, water, mushrooms and zucchini and bring to a boil. Reduce heat to a simmer and cook until vegetables begin to get tender, about 10-15 minutes.
Gently add the tofu to the skillet in small portions. Cook over a low simmer for an additional 5 minutes.
Season with salt if needed, and top with thinly sliced scallions and sesame seeds. Enjoy!