Heat a large cast-iron skillet over medium-high. Season the steak with 1/2 teaspoon each salt and pepper.
Add olive oil to the skillet and cook steak for 2–3 minutes per side for medium-rare, depending on thickness. Let rest on a cutting board for 5 minutes, then slice against the grain.
Smash cucumber halves with the side of a chef’s knife, then cut into 4–6 chunks per piece. Place in a bowl and toss with 2 tsp salt. Let sit for 10 minutes.
In a separate large bowl, whisk together sesame oil, sesame seeds, soy sauce, lemon juice, ginger, and honey.
Rinse cucumbers in a colander, shake off excess water, and toss with dressing and chopped cilantro.
Serve the steak slices alongside the cucumber salad. Drizzle with chili crisp if desired.