Heat one tablespoon cooking oil in a frying pan.

Spread the onion slices in the hot oil and sprinkle with salt and pepper.

Cook over medium-low heat, stirring often after the first two to three minutes, until caramelized and softened.

Scoop out the caramelized onion and set aside.

Preheat the broiler to 400F.

Heat another tablespoon of cooking oil in the pan.

Spread the julienned bell pepper in the hot oil and sprinkle with salt and pepper.

Cook over medium heat, stirring occasionally, until softened and the edges are starting to brown.

Scoop out the bell pepper and set aside.

Drizzle the remaing oil into the pan, add the butter, and set the heat to high.

Sear the beef with salt and pepper on high heat, stirring the pieces around once the meat is no longer pink.

Split the rolls, and spread butter on the cut side of both the top and bottom halves.

Divide the beef into three portions.

Arrange the rolls (including the top halves) on a tray.

Arrange one portion of beef on each of the bottom halves of the rolls, and top with caramelized onion and bell pepper.

Lay cheese slices on top of the beef, onion and bell peppers.

Heat in the broiler just until the cheese melts.

Serve the pepper cheesesteak sandwiches immediately.