It's wonderfully amazing...the food i grew up with is now spreading out to many different regions. i don't know why this is usually eaten during lent, but i know everyone in the mexican/american community eats this....and believe me---there are soooo many different variations!
my grandmother would use sliced white bread, sliced yelloe cheese, canela, and raisins. Some people use piloncillo, prunes, peanuts, walnuts, etc. She'd serve this as a dessert to her Lent meal which was shrimp patties made with dried, ground shrimp and some kind of corn thing with chile on it.
My mom (who does not like to cook or bake) once made a simple version. She boiled some canela sticks and raisins in water, then toasted the sliced bread in a toaster, layered all the bread and cheese in a large dish and poured the water with the raisins all over it and baked it. I can't tell you all the measurements etc but just look it up on recipezaar or something like that. You MUST try it! They even serve it at my small hometown's school as a dessert during lent!