Realistic 3D model of a gourmet burger: a golden-brown sesame seed bun (top and bottom) slightly shiny, crisp lettuce leaves, a juicy beef patty with grill marks, melted cheddar cheese over the patty dripping slightly, a slice of tomato peeking out, a few rings of red onion, some sesame seeds on top bun, soft shadows, natural lighting. Photorealistic, high resolution, full colors, slightly stylized but realistic food render, ready for 3D export.