A robust rub adds major flavor to lean, quick-cooking pork tenderloin. The finely ground coffee lends a pleasant bitter note that is tempered by brown sugar and dried spices. The addition of green beans makes this a one-pan meal that can be on the table in no time at all.
Position an oven rack in the top third of the oven and preheat the broiler to high.
Combine the coffee, brown sugar, 1 1/2 teaspoons salt, 1 teaspoon black pepper, garlic powder, crushed red pepper, cumin and paprika in a small bowl and mix well. Drizzle the pork tenderloin with 2 tablespoons olive oil and evenly sprinkle the rub all over, patting to adhere. Let marinate at room temperature for 30 minutes.
Toss the green beans in a large bowl with 3 tablespoons olive oil, 1 teaspoon salt and 1/4 teaspoon black pepper until well coated.
Put the pork in the center of a large cast-iron skillet or heavy ovenproof skillet and scatter the green beans around it. (The pork should be directly on the pan, not on top of the green beans.) Broil for 10 to 12 minutes, flipping the pork and tossing the green beans halfway through cooking. When ready, an instant-read thermometer inserted in the center of the pork should register 145 degrees F and the green beans should be tender and lightly charred.
Allow the pork to rest for 10 minutes before slicing across the grain. Serve with the green beans.