To make the dressing, add all of the ingredients to a small bowl and whisk to combine. Set aside until ready to serve.
Spray the steak with olive oil and season both sides with 1 teaspoon salt, pepper and the cumin.
Add the peppers and onions to a mixing bowl and drizzle with the remaining 2 teaspoons of oil. Toss them to coat them in the oil, but be careful not to separate the onion rings.
Preheat the grill to medium high heat and lightly oil the grates. Place the steak on one half of the grill. Cook for 5-7 minutes per side until the steak is 125 degrees F. Remove the steak from the grill and let rest for 10 minutes.
Simultaneously, add the peppers and onions to the other side of the grill in an even layer. Cook, turning as needed, until the vegetables are nicely charred and soft, about 10 minutes. Remove the veggies from the grill and let rest until cool enough to handle.
To serve, slice the peppers into strips and place on top of the chopped romaine. Separate the onion slices into rings and place them on top of the peppers. Slice the steak against the grain and shingle it on top of the vegetables. Top with avocado and cilantro and drizzle with the dressing.
