Cut the cabbage into thin strips perpendicular to the fibers. Mince the green onion.

Lay out each pork belly slice, season with salt and pepper, and place 1/10 of the cabbage on each slice. Roll tightly from one end to form 10 rolls. Arrange them on a heatproof plate, drizzle with sake, cover with plastic wrap, and microwave at 600W for 5 minutes. Let sit for 1 minute to finish cooking with residual heat.

Mix minced green onion with salt, lemon juice, sesame oil, and white sesame seeds in a bowl to make the negi salt sauce.