Prepare the marinade by mixing the olive oil, lemon zest, oregano, and crushed fennel seeds. Coat the cubed lamb entirely with this mixture and allow it to marinate for anywhere from two hours to overnight to mellow the lamb flavor.

Melt the butter in a cast-iron skillet over high heat. Add the sliced red onions and sear them for about ten minutes until they develop a rich color. Once done, remove the onions from the pan and set them aside.

Take the lamb out of the marinade and shake off any excess oil. Make sure the meat is cubed properly, then season it thoroughly with a tablespoon of sea salt and black pepper.

Assemble the radish pico by tossing together the finely diced radishes, chopped cilantro, diced jalapeño, and diced Roma tomatoes with a pinch of sea salt.

Sear the seasoned lamb in the hot skillet on all sides for 6 to 8 minutes; it needs a good outer crust but does not have to be completely cooked through. Return the caramelized red onions to the skillet and toss to combine. Move the lamb mixture to the side and crack the eggs directly into the skillet, cooking them alongside the meat to absorb all the rich pan flavors. To build the tacos, char the corn tortillas on a grill, layer them with the cooked egg and seared lamb, top with a spoonful of radish pico, and complete with a fresh squeeze of citrus.