Grind coriander and cumin seed in a spice grinder, coffee grinder or mortar and pestle and place in a medium sized bowl.
Add garlic, oil, hot sauce and mustard and stir.
Place the steak into a resealable freezer bag and pour in the marinade.
Seal and rub the marinade into the meat, making sure it’s well coated. Put in fridge for at least 1 hour, or as long as overnight.
Heat a large cast iron skillet over medium-high heat.
Turn and sear on other side for 5 minutes more, or until steak is medium rare.
Let the steak rest for 5 minutes, and then slice thinly across the grain of the meat.
Place salad dressing ingredients into the bottom of a salad bowl and whisk together.
Add greens, cilantro, red pepper, grated cheese, and flank steak to the salad bowl. Toss well and serve.
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