In a medium bowl, whisk together the orange juice, lime juice, garlic, cumin, and olive oil. Season to taste with salt and pepper. Add the diced beef to the marinade; turn to coat. Cover and let rest at 1 hour. 

While the steak marinates, prepare the onions. Add the sliced onions, vinegar, honey, and a pinch of salt to a small pot. Bring to a boil over medium heat. When the liquid starts to boil, remove from the heat and let cool. 

Heat a heavy pan, preferably cast iron, over high heat. Use tongs or a slotted spoon to transfer the meat from the bowl to the hot pan, leaving the marinade behind. Cook 4-5 minutes, or until the steak bites are browned on the outside and medium or medium-well inside. 

Divide the steak among 12 lettuce leaves. Top with pickled onions, diced avocado, and cilantro. Serve with lime wedges.