Pat 1 8oz steak dry with paper towel. Add 1 tbsp coffee, 1 tbsp cracked black pepper and 1 tbsp salt in a small bowl. Mix to combine, then season the steak all over. Let sit at room temperature for 30 minutes, or as much time as you have (up to 2 days in the fridge).
Heat a cast iron on medium-high heat until just before it starts to smoke, about 3 minutes. Add 1 tbsp canola oil and let heat up, another 30 seconds.
Add steak and cook on medium-high until a dark golden brown crust forms, about 3 minutes. Try your best not to move it around during this initial sear, just let it do its thing! Flip and cook the other side for another 3 minutes. Rotate the steak to grill remaining sides for about 30 seconds each, if your steak has a fat cap, cook that side for a little longer, about 1 minute.
Remove from heat. Add 2 tbsp butter and baste the steak for two minutes. By now, an instant-read thermometer placed in the thickest part of the steak should be 120-130°F. Remove from the pan and let it rest on a cutting board for about 10 minutes.
While the steak is resting, put the pan back on the heat and turn to medium-high. Once it heats up, add the shishitos and let cook. After a few minutes you should start to hear sizzling and popping — this means the peppers are beginning to blister. Toss and let cook until the peppers are golden brown and charred all over, about 3 minutes.
Reduce heat to medium-low and add the juice of half a lemon. Toss and continue cooking on medium until soft, about 4-5 more minutes. Transfer to a cutting board and roughly chop until the peppers form a salsa-like consistency.
Cut your steak into strips and top with chopped peppers and a sprinkle of flaky salt. Serve hot.
