Heat oven to 400F and place rack in top third of oven.

Heat oil in a big skillet or cast iron pan.

Sauté bell peppers and onions until they are the desired softness. Remove from pan.

Heat the skillet over high heat until it is very hot.

Add the steak and sear until it’s nicely browned on one side, then flip over and let cook just until the meat is almost done. This will be done pretty fast if your pan is hot enough. You don’t want to cook it so slow that it doesn’t brown or overcooks. Don’t overcrowd the pan or it won’t brown. I do mine in two batches.

Slice the baguette in half lengthwise, then in half crosswise so it fits in the baking pan. You can pull out some of the inside of the bread to make a little nest to hold the toppings, especially if your bread is thicker. You can also just press down the insides of the bread, as I have done in the photos.

Spread a little mayo on the bread, if using.

Layer the provolone cheese on top of the bread, then the peppers and onions, then the steak, then the cheddar cheese.

Heat the bread on a baking sheet on the top rack of a hot oven for a few minutes until the cheese is nicely melted.

Serve whole or cut up into appetizer-sized pieces.