Cut the yuzu in half. Peel one half, remove the white pith, and slice into thin strips. Squeeze the juice from the peeled half. Cut the remaining half into wedges for topping.

In a pot, combine the broth ingredients (water, dashi powder, salt, soy sauce, and grated ginger) and heat over medium heat. Once boiling, add the frozen udon and cook according to package instructions. Add the yuzu peel and juice, then turn off the heat and mix gently.