Prepare ingredients per instructions above.
Preheat the oven broiler.
Lightly toast the rolls on a baking sheet. Spread mayo inside the roll optional.
Heat half of the olive oil in a skillet over medium heat. Sauté the onions and bell peppers until golden brown and caramelized, about 5 minutes. Transfer to a plate and set aside.
Add the remaining olive oil to the skillet. Add the shaved steak in an even layer and let it brown undisturbed for 2 minutes. Sauté until fully cooked through and season with salt and black pepper to taste.
Divide the steak into portions in the skillet. Top each portion with cheese. Melt under the oven broiler.
Place each portion of steak into a roll. Cut in half if preferred.
Add lemon slices to sparkling water.
Serve the Philly cheesesteak with berries, pickle, and lemon sparkling water