Mix cumin, coriander, chili powder, salt and 3/4 tsp. pepper in a small bowl. Rub steak with the cut garlic. Rub the spice mix all over the steak. Heat 2 tsp. oil in a large heavy skillet, preferably cast iron, over medium-high heat. Add the steak and cook to desired doneness, 4 to 6 minutes per side for medium-rare. Transfer to a cutting board and let rest. Add remaining 1 tsp. of oil to the skillet. Add bell peppers and onion; cook, stirring often, until softened, about 4 minutes. Add minced garlic and brown sugar; cook, stirring often, for 1 minute. Add coffee, vinegar and any accumulated meat juices; cook for 3 minutes to intensify flavor and season with pepper. To serve, mound 1-cup watercress on each plate. Top with the sautéed peppers and onion. Slice the steak thinly across the grain and arrange on the vegetables. Pour the sauce from the pan over the steak and serve immediately.
Ready in 35 minutes