Juice your fresh limes and the large orange. Fresh juice is much better than the bottled kind. It helps break down the tough meat fibers.

Chop the fresh cilantro and the garlic cloves. Make sure the garlic is minced very small. This helps the flavor spread evenly in the bag.

Whisk the olive oil and citrus juices together. Add the minced garlic and the chopped cilantro. The mixture should look very green and bright.

Stir in the cumin, oregano, and chili powder. Add the salt and the black pepper next. These spices give the meat a smoky depth.

Add the minced jalapeño if you like spice. Remove the seeds to keep the heat very mild. Stir well so the peppers are mixed in.

Place your steak into a large plastic bag. Flank steak or skirt steak works the best here. These cuts soak up the marinade very well.

Pour the marinade into the bag with meat. Squeeze out the air and seal it tightly. Massage the bag to coat every inch of meat.

Put the bag in the fridge for 4 hours. You can leave it for up to 24 hours. This makes the steak very soft and flavorful.