Malu Calixto´s Sandwich

This "Rapidinha" (quickie stuff) is idea of my friend Malu Calixto, who just arrived in the country of my favorite beer, Guinness (Ireland).
She said the recipe is made since she was a child.
Bread with mayonnaise, many thin slices of tomato, seasoned with a little salt and oregano. She leaves warm in the oven ... That's it.
Who like ketchup, can put a little bit. Is delicious, ensures Malu.