In a bowl or resealable bag, combine the olive oil, lime juice, minced garlic, chipotle peppers, ground cumin, salt, and black pepper to create a zesty marinade. Add the sirloin steak, ensuring it's fully coated. Let the steak marinate in the refrigerator for 10-20 minutes for maximum flavor absorption.

While the steak is marinating, wash and slice the bell peppers and onion into thin strips. Prepare any additional toppings like tomatoes, corn, and black beans by rinsing and draining as necessary. If you're using uncooked rice, start cooking it.

Heat a large skillet over medium-high heat, and add a splash of olive oil. Once hot, add the marinated steak to the skillet, cooking for about 3-5 minutes on each side to your desired doneness. Remove the steak and let it rest.

Using the same skillet, add the sliced bell peppers and onions over medium heat. Sauté until tender and slightly charred, around 5-7 minutes, stirring occasionally.

In a medium bowl, mash the two avocados until smooth, then mix in a pinch of salt and minced jalapeños.

To assemble, start with a base of shredded romaine or rice. Layer with sautéed bell peppers and onions, then add sliced steak and finish with toppings like guacamole, corn, diced tomatoes, black beans, and sour cream.