In a large frying pan, heat olive oil over high heat and drop the steaks in, one at a time. Cook the steak for 1 minute on each side.
Remove the steaks from the pan and drop the heat to low. Add to the same pan the lime juice of one lime, onions and garlic.
Stir the onions constantly until they're translucent and cooked through
Carefully cut your cuban bread loaf approximately the length of your bistec and the slice it in half. Place the tomatoes down first and on top place your cooked palomilla steak. This allows all the juices from the steak to get soaked up by tomato while simultaneously preventing your bottom piece of bread from getting soggy.
Over the steak place your grilled onions.
Over the onions place your lettuce, tomato and potato sticks.
Place the top of the cuban bread over the sandwich and brush some melted butter over the top bun if desired.