In a moderately heated frying pan, fry the bacon, it needs to be cooked, but not crispy.
Gently fry the egg, you want the yolk running but all the white cooked through.
Build the sandwich with the bread first, then the bacon, on the bacon add the egg, yolk up. Put the the tomato sauce on the other slice of bread.
You can simply make the sandwich now, leaving it booby trapped for when you bite into the yolk, or you can burst it and spread around, placing the bread with the tomato sauce on it now creates a wonderful flavour. Eat as soon as possible.