Pour the warm water into a bowl and add the yeast. Whisk it together and leave for five minutes.
Next, add salt, flour, and oil, and mix thoroughly.
Transfer the dough mixture onto a floured work surface and knead with your hands for three to five minutes until you get a smooth and elastic dough.
Transfer the dough to a bowl greased with olive oil, cover with plastic wrap or a light kitchen cloth and leave to rise for an hour at room temperature (or until doubled in size).
Meanwhile, preheat your oven to 425 degrees F.
Once the dough has risen, lightly punch it down and divide it into four equal portions.
Stretch the dough and roll it into a circle.
Add shredded cheese in the middle, then place eight pepperonis on top.
Fold the calzoni in half and pinch the ends together.
Repeat for the other three portions.
Place the calzonis on a sheet pan lined with parchment paper and bake for 15 to 20 minutes.
After the calzonis are baked, brush the tops with melted butter and sprinkle Italian seasoning on top.
Serve with marinara sauce on the side and enjoy.