Heat a cast-iron or stainless-steel pan over high heat until hot.
Add enough oil to lightly coat the pan. Once the oil begins to lightly smoke, carefully place in the steak.
Flip every 30 seconds for even browning and crust development. You can place a meat thermometer to check the doneness, or you can use your fingertips.
Remove the steak from the pan and rest for 5–10 minutes.
While the steak rests, chiffonade the lettuce (roll leaves, then slice thin). Quarter the Roma tomatoes, remove seeds, and cut into smaller pieces.
Julienne the bell pepper (thin matchstick slices). Slice and cube the avocado.
Combine all in a bowl and lightly toss with the vinaigrette.
Slice the rested steak against the grain into strips. Plate alongside or over the salad.
Optional: Place sliced steak over a crisp tostada, top with salad, and enjoy for a crunchy, refreshing twist!