Slice enough pieces of bread per the number of eggs each person would like.
Crack the egg into an individual custard cup. Set aside.
Butter both sides of the bread.
Using a biscuit cutter, the rim of a buttered glass or a donut cutter (center piece removed), carefully cut out a hole in the center of the bread. Keep the center as you'll be using it later. [If you accidentally end up splitting the crust, cut another piece of bread and start over otherwise the egg will leak outside the bread. Save the broken piece for another use like breadcrumbs.]
Heat a cast iron skillet over medium heat. Once heated (the edge will be warm), lay your bread into the skillet. Let it cook for a minute or so.
Add the cut round of bread to the skillet to toast along with the tomatoes if using.
Into the center of the hole, swirl 1 teaspoon of pesto until its warm and heated.
Gently pour the egg into the center of the bread. Cook for 2-3 minutes or so until the bread is toasted on the bottom. The egg will appear cooked white through on the bottom and clear on top. A spatula will also under the bread easily. That's when you know its ready to be flipped.
Flip the bread over and cook on the other side until the egg is cooked through about a minute or more.
Serve hot. Mangia!