Combine chopped garlic, chopped onion, fresh orange juice, and fresh lime juice in a bowl.

Heat olive oil in a large saucepan until just smoking.

Carefully pour the contents of the bowl into the hot oil.

Simmer for 5 minutes to soften the onions and garlic.

Season the marinade with kosher salt, black pepper, ground cumin, dried oregano, and chopped fresh cilantro.

Transfer the mixture to a blender or food processor and pulse 3 times to combine.

Pour the marinade into a plastic container and cool to room temperature.

Cover and refrigerate for up to 2 weeks.