Place ¾ cup warm water, yeast and sugar in a small bowl; let sit for 5 minutes or until active and bubbly. While waiting, prep dough ingredients.
In a stand mixer, combine flour, xanthan gum, baking powder and salt. Whisk to combine. Add yeast mixture, eggs and oil to the flour mixture. Blend on medium speed using a dough hook.
Add an additional ¼ cup water as needed, 1 tablespoon at a time, to achieve a sticky yet touchable dough. You should be able to touch the dough without having it stick to your finger. Knead in the mixer for 5 minutes.
In a large bowl, combine Italian seasoning, garlic powder and Parmesan cheese. Generously spray a 12-cup Bundt pan with oil. Scoop ⅓ of the dough into tablespoon-sized balls with a small cookie scoop into the Parmesan cheese mixture. Toss gently with a fork to coat. Evenly distribute them into the prepared Bundt pan. Next add ⅓ of the cheese and pepperoni. Continue until you have three layers, ending with the remaining cheese. Cover the pan with a towel and place in a warm place until doubled in size, about 1 hour.
Preheat oven to 350°F. Pour melted butter over the risen dough, place on a sheet pan to hold any drips and bake for 30-40 minutes. The bread will be golden brown and set, but still give a little when pressed. Allow to cool for 3 minutes in the pan, and then turn out onto a platter.