In a large mixing bowl, gently combine the lump crabmeat, mayonnaise, Panko, flour, egg, sliced green onions, finely diced red bell pepper, Worcestershire sauce, Cajun seasoning, and lemon juice. Be careful not to break up the crab too much; you want to maintain those lovely lumps.
Using your hands, scoop out a portion of the mixture and form it into a patty about 2 inches in diameter. Repeat this process until all the mixture is shaped into crab cakes. You should have about 8 to 10 cakes, depending on the size.
Place the formed crab cakes on a plate and cover them with plastic wrap. Refrigerate them for at least 30 minutes. This step helps the cakes hold their shape during cooking.
In a large frying pan, heat the vegetable oil over medium heat until shimmering. The oil should be hot but not smoking.
Carefully add the crab cakes to the hot oil, making sure not to overcrowd the pan. Fry for about 4-5 minutes on each side, or until they are golden brown and crispy. Use a slotted spatula to flip them gently.
Once cooked, transfer the crab cakes to a plate lined with paper towels to absorb any excess oil. Serve immediately with your favorite dipping sauce, a squeeze of lemon, or a side salad.