Get your briquettes hot in the charcoal grill or use campfire coals. Lay the pie iron in the coals to pre-heat it on both sides.
When the pie iron is hot, remove it from the coals and butter the interior with the margarine, using a cooking brush. Make sure to butter the edges as well, where the two halves of the pie iron clamp together. It will smoke some as you brush on the margarine but that's fine.
Lay one side of the greased pie iron face up and lay a slice of bread on it, pushing it in a bit to fit. The edges will extend beyond the perimeter of the pie iron slightly but that's okay.
On the bread, sprinkle on a good bit of mozarella cheese, then layer on about 10-12 thin slices of pepperoni. Next, pour on just a little of the tomato sauce, (use regular tomato sauce if you don't want it spicy), and then top it with a tomato slice. Cover this with another slice of bread and close the pie iron with the greased top half of the unit.
You will have to compress the pie iron a bit to close it and you'll find that there's a hook attached to the handles to keep it closed while baking in the hot coals.
Now, lay the pie iron firmly down in the hot coals for TWO MINUTES. Then flip it over and allow it to cook on the second side for TWO MINUTES. Time is pretty critical to avoid burning the calzone.
At the end of the second two minutes, take the pie iron to where you can open it and extract the calzone to a plate. You can use a butter knife to loosen any stubborn ones. Be careful to not burn yourself -- an adult should do this step of the process.
With a sharp knife, carefully trim off any burnt edges (the calzone should be golden brown -- adjust your time on subsequent servings to achieve the desired doneness), allow to cool for a couple of minutes and then cut the calzone in half on the diagonal -- serve warm.
NOTE: You can vary the ingredients all you want -- here are some great variations: You can use 4 small tortillas instead of the bread, with butter or cheese in between layers, 2 flour tortillas and 2 corn tortillas make for a nice flavor and presentation; for different fillings, try canned Skyline Chili and hot dog slices with cheese and fancy mustard; any sort of pizza toppings with pepperoni; thick sausage gravy; scrambled eggs, a canadian bacon slice and syrup, or; blueberry pie filling. Also, vary the cheeses to add more zest -- I like adding freshly grated parmesan to the mozarella sometimes. Hot pepper cheese and Swiss Cheese are also good choices. You are limited only by your imagination on the fillings that you choose -- Enjoy!
TIP: I like to have all my fillings at room temperature when I begin.