In a bowl, add minced garlic, sour orange juice, dried oregano, ground cumin, salt and pepper.
Put the skirt steak in a shallow dish or a resealable plastic bag and pour the marinade over it, by ensuring that the steak is fully coated.
Put it in the refrigerator to let it marinade for at least an hour or up to 8 hour for better flavor.
Remove the steak from the marinade and dry it using paper towels.
In a large skillet, heat 2 tablespoons of olive oil over medium-high flame. Cook the steak in the skillet until thoroughly cooked and brown, it may take around 4-5 minutes per side.
Take the steak out from the skillet and let it rest for a few minutes.
In the similar skillet, add a little more olive oil if required. Add the sliced onions and cook them until turn soft and brown, it may take around 6- minutes.
Mix in the lime juice and cook for more 1-2 minutes.
Slice the rested steak thinly against the grain. Return the steak to the skillet with the onions and mix them together.
You can top it with fresh cilantro or lemon wedges on the side.