Chop the chipotle peppers and garlic together until they are finely minced and add them to the mayonnaise.
Stir in the vinegar, molasses, onion powder, cumin, salt, and pepper. Set the aioli aside.
Grill the onions and peppers
Heat the oil in a large skillet over medium heat.
Add the onions and peppers and cook for 15 to 20 minutes, stirring occasionally, until the onions are golden brown. Season with salt and pepper
Assemble the sandwiches
Toast the hoagie rolls under a broiler or lay them flat on a grill until lightly browned.
Slice the tri-tip steak into thin slices. Cut across the grain to get tender slices of meat.
Spread the chipotle aioli onto the toasted buns then pile the onion and pepper mixture on one side. Top the onions with two slices of cheese then a heap of sliced tri-tip.
Notes
Make the aioli ahead: The chipotle aioli keeps for up to a week in the fridge and tastes even better after a day or two.Use leftover tri tip: This sandwich is a great way to repurpose leftover grilled or roasted tri tip—just slice it thin and reheat gently.Control the heat: Start with one chipotle pepper in the aioli and taste before adding more. Some cans pack serious punch.Cheese swap: Monterey Jack melts beautifully, but provolone or pepper jack work just as well.Toast matters: Don’t skip toasting the rolls. It keeps them from getting soggy and adds extra texture.Leftover tri tip? Slice it cold and toss it into our tri tip salad for a fresh lunch the next day.