Heat a cast iron skillet over medium heat.
Take two slices of bread, spreading a thin layer of butter on one side of each slice.
Turn the buttered sides over and spread a layer of pesto on the other.
Top with 1/2 cup of mozzarella, slices of tomato, a few basil leaves, and sprinkle with oregano, salt, and fresh ground pepper.
Close the sandwich with the buttered sides out, cook in the skillet until each size is toasted to a nice golden color and the cheese is completely melted.
Pour your favorite marinara into a small ramekin for dipping.