To marinate the steak, place steak in a gallon sized plastic bag, add cumin, tamari and salt. Massage meat and let marinate in the fridge for 2 hours.
Preheat an oven to 400 F. In the meantime, cut cauliflower head in half and cut half into florets. Place in a large mixing bowl and add 2 T olive oil and ¾ t salt. Toss to coat well. Place baking sheet in the oven to preheat with the oven. Once pan and oven are hot, add 1 T olive oil to the baking sheet then toss on oiled cauliflower. Let them roast for 20-25 minutes until soften and browned on the edges. Let cool slightly.
Preheat a grill until it reaches 500 F. Place flank steak on hot grill. Close the lid and let it cook this way for 8-10 minutes. Then turn flank steak at a 90 degree angle and place it on the same side to create a hatch mark pattern. Let this cook for another 3-5 minutes with the lid closed. Flip the flank steak and cook it until it reaches about 135 F on the inside using a thermometer to check temperature. Let the meat rest for 10 minutes before cutting into it.
Combine 1 T olive oil and 1 T vinegar for the dressing adding in ¼ t salt.
Toss the roasted cauliflower with the greens and dressing. Taste and adjust seasoning as you like.
Slice the meat into thin strips and serve on top.