MAKE THE HERB SAUCE: In a blender or food processor, pulse the parsley, cilantro, mint, green onion, garlic, lemon juice and olive oil until completely smooth. Set aside.
MAKE THE CAULIFLOWER STEAKS: With a sharp knife, cut the cauliflower into 1-inch-thick slices. (You should get about 8 slices.) Rub both sides of each piece of cauliflower with about 1 teaspoon olive oil. Sprinkle both sides of each piece with 1/2 teaspoon smoked paprika, salt and pepper.
Heat the remaining 1 tablespoon olive oil in a large cast-iron skillet over medium-high heat. Working in batches, sear the cauliflower steaks until they are golden brown, 3 to 4 minutes per side. The cauliflower should be easily pierced with a fork but not so tender that it falls apart.
To serve, place 2 cauliflower steaks on each plate and top with a generous drizzle of the lemon-herb sauce. Serve immediately with steamed wild rice.
Leftover sauce will keep in the refrigerator for up to a week.