To make the po' boy:
1. In a heavy pot or a fryer, add oil and heat to 375 degrees.
2. In a medium-sized bowl, combine cornmeal, flour, salt, cayenne, and black pepper. In a small bowl, lightly beat the eggs. One at a time, dip the oysters into the egg mixture, then coat in the cornmeal mixture. Fry in small batches, until oysters are golden on both sides, about 2 to 3 minutes. Drain on paper towels.
3. To assemble the po’ boy, slather the bottom bun with the tartar sauce, or mayonnaise, and layer with lettuce, 2 oysters, a squeeze of lemon, a half slice of tomato, and top with bun. Serve immediately.
To make the tartar sauce:
1. In a small bowl, mix all the ingredients together. Season to taste with salt and pepper.